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Your RV Generator and How It Works

Don is a retired engineer and long-time motorhome owner who enjoys helping readers deal with the increasingly complex technology of RVs.

How the Generator in Your RV Works

I had a guy ask me one day; "OK, I am not in the least a technical person, so how does a generator work? All I know is if it gets fuel, it runs and I get electricity out of it."

I thought about this poor guys problem and i realized that he had a valid complaint. He doesn't need to be an engineer, but he does need to understand the basics on how a basic generator operates. So, I wrote this article hoping that it will give you a basic overview of the different designs of RV generators, how they operate, and some basic generator service tips.

It will also describe basic differences in gas-powered generators and diesel-powered generators and how they function.

This knowledge may one day help you determine the cause of any generator problems you may have.

A History of RV Generators

In the early days of camping in the USA, there were “rough campers.” For these people, "camping" included a tent, a sleeping bag, a backpack of dried foods, bottled water, a few matches, a snake bite kit, and not much else.

And you know what? I've been there, and I've done that!

It was fun! Especially when I was young, healthy, strong, and had very little money.

And, later in life, when I was first married, and we had kids, I "rough camped" for a while. We camped at resorts, at beaches, and in the mountains. We used larger tents, nicer sleeping bags, inflatable mattresses, a small cooking grill, several coolers for real food, and a few more accessories. And that was fun too, again, for a while!

After a few years, we purchased our first Tag-Along camper. It had rudimentary plumbing, electric lights, storage cabinets, a "porta-potty,” all more comforts for dealing with the vagaries of the weather, and then, of course, we had even more accessories to make our camping more fun.

Those first old campers of ours, way back then, had your basic accessories, such as electric lights, a water pump, a propane stove, but not a whole lot else. They did not have such things as television, air conditioning, hot water heaters, microwave ovens, and all of the amenities that you will find as standard equipment on the RVs of today.

RV and Motorhome Batteries

We owned our couple of travel trailers in the 70's (yeah, way back then) . Probably the biggest problem for us then was that they did not have a generator, just a COACH battery. This battery was usually a deep-discharge 12-volt DC battery that was the same design as what is used in an automobile.

It was usually tied down onto the front end of the travel trailer and was protected from the elements in a plastic case. Typically, you charged the battery up before you left home.

And, considering it only had to power a few 12-volt interior lights, and maybe a small water pump to provide water at the miniature sink, it was a more than adequate power system for a good week of fun.

Over time, as some campgrounds began to provide 115-volt AC at your site, camper manufacturers added small, efficient AC-to-DC converters, so you could charge your camper battery at the campsite.

And once you had an RV with AC as well as DC power, the camper designs used dual-mode light systems (110-VAC and 12-VDC), as well as connections for small appliances.

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RVs even began to include showers, electric hot water heaters, larger water pumps, microwave ovens, TVs and multiple wall receptacles for the campers convenience..

RV Battery Box

Appliances for Motorhomes Created a Demand for Generators

The most important electrical addition manufacturers made to RVs and campers was extra electric receptacles, in the kitchen, bathroom, bedroom, and so on.

Once the power was accessible throughout an RV, people started bringing their favorite appliances from home, such as coffee makers, hair dryers, toasters, portable TV's and radios, and on, and on, and on.

RV manufacturers had to react by adding electric breaker panels (versus those old fuses) to handle potential overloads, and heavier wiring for the current all these appliances pulled.

Eventually campers became accustomed to using such appliances everywhere: in state parks, in the woods, alongside streams and lakes, and pretty much wherever they went.

So, the next "necessary item" for the typical modern camper was—you got it—a good electric generator. We all wanted those conveniences and therefore that power, everywhere, all of the time. At the flick of a switch!

Underside of an RV generator (the red fluff is a shop rag that got sucked into it).

Underside of an RV generator (the red fluff is a shop rag that got sucked into it).

Why Have a Built-In RV Generator?

Today, the average RV owner travels much further to reach their camping destination than even a decade ago.

On these longer trips, they often have to stop for the night at an interim campground or two along the way, or do the Wally-World thing (overnight in their parking lot?), or stop and sleep at a rest stop or other public parking lot. And the next morning they eat, pack up, and hit the road for the next part of their trip.

Of course, while on these longer trips they usually have a fridge that is packed with fresh food and beverages, and so they are able to eat very good meals and then sleep in that comfortable bed in the camper.

Myself, I have pulled into a rest area around 6-7 PM, fired up my generator, turned on the TV for local news and weather, eventually cooked a light dinner, and watched my favorite network TV shows, all with the AC running, and finally I'd go to sleep in my nice cool camper, on my own bed.

Often, in a rest area, I will leave the generator running all night, along with a couple of roof fans, recharging my house batteries and providing just enough background noise to drown out most of the outside noise from the comings and goings of other vehicles, campers, and truckers in the rest area.

I will get up in the morning, make fresh coffee, toast a muffin, and boil or fry an egg for a hot breakfast, maybe even take a hot shower, all before I shut down my generator and continue my trip.

Now I have a motorhome, with a built-in generator that is designed especially for the appliances in my RV. It is ridiculously easy to operate. And, often, parked right beside me, might be a Class-C, a Fifth-Wheel, or a Tag-Along, all with their own built-in generators, providing those creature comforts we are all spoiled with. Ain't camping life a rough life?

Portable Generators Came First, Then the Built-In RV Generator

Before camper owners started buying their RV with a built-in generator, many of them used portable generators.

They were convenient, and reliable. But they took up a lot of room when it came to storing them.

And not many models were quiet enough for use at night in a campground.

Because by this time the RV manufacturers knew that they had to do whatever as necessary to make their motorhomes more competitive than the others, they all started installing built-in generators in the larger motorhomes.

So, Now We Can Talk About Generators and Motorhomes

Built-in generators are so popular today that it's actually hard to find a motorhome that doesn't come with a nice generator built into it.

Why only in motorhomes, you might ask, and not in towable campers?

Well, a motorhome already has a fuel source for its engine, so the generator can be fueled by the same tank as the engine.

You rarely see a towable camper with a built-in generator, because to install a generator the manufacturers would have to install a fuel tank as well.

Troubleshooting: Reasons Why Your Generator Might Not Start Up

1. Fuel Supply

Every motorhome manufacturer today that includes an electric generator in their design also includes one little innovation: that is, they no longer attach the fuel line for the generator to the bottom of the RV’s main fuel tank.

They attach it now about a quarter of the way up from the bottom of the tank, so that it will only pick up fuel if the main fuel tank is more than 1/4 full.

This redesign was intended to avoid the situation where a camper out in the middle of nowhere runs the generator until it uses up so much fuel that there isn’t enough left to drive the vehicle back to a gas station and fill it up again.

So, if you are out somewhere rough camping and your generator won't fire up when you turn it on, check that your fuel tank is more than 1/4 full. And if your rig is parked on a slant, the tank may have to be even more than 1/4 full for the fuel level to reach the line to the generator.

2. Oil Supply

Many built-in generators won't start if the oil is down to one quart or less. And that's one reason why you should check the oil in the generator often.

3. 12-Volt Power Switch

To get started, your built-in generator needs power from the 12-volt Coach battery system in your RV. If the power switch to the coach's 12-volt accessories has been turned off, for example to prevent power drainage while the vehicle is in storage, the generator can't get power. Many RV owners don't know where this cut-off switch is. Find it and check it.

4. Fuel Pump or Fuel Filter

If the generator won't run, or runs sluggishly, and there are no fuel, oil, or connection problems, the generator itself may be bad.

But the problem is usually the fuel filter (which can become clogged, especially when using diesel). Fuel filters are common culprits but they are pretty cheap to replace.

Understand How Your Generator Works!

If you use an electric generator, you should have at least a general understanding of how it works, so that you can make sure your generator is there for you when you need it.

First of all, it has to start, easily and quickly. Then it has to run, smoothly, automatically, and efficiently.

Here are some basic facts about generators.

There are four basic functional sections of an electric generator. Of course you can tear a generator down to smaller and smaller working pieces, but I am not trying to teach you to be a mechanic, rather I want you to know how one functions from a high level.

That way you will understand the importance of those pesky preventive maintenance parts in a generator, and why they need to be monitored and even replaced occasionally.

The four functional parts of a generator are:

  1. a fueled mechanical motor
  2. a fuel supply system
  3. an electric starter motor
  4. an electric power generator

1. The Fueled Motor

Generators are run by a fueled motor of some kind, usually gasoline or diesel, as I have mentioned.

The motor uses the combustion of the fuel to keep the crankshaft of the motor turning.

Today, there are many different designs of motors, from the simple to the complex. An example I can describe here is a simple, cheap gasoline-powered lawn-mower motor with two cylinders.

Each cylinder contains a piston which is connected to a crankshaft. Each cylinder has a fuel input port and an air input port, as well as an exhaust port. The two cylinders are designed so that when one cylinder is firing, the other one is getting fuel and air to fire.

This whole assembly is mechanically designed so that you will get continual firing and exhaust, and the crankshaft will turn from all of this combustion action in the cylinders.

In a diesel motor, there is no spark plug; the combustion is achieved via high compression of the diesel fuel.

Lubrication

One of the most important things to watch is your generator motor's lubrication. Your generator motor uses oil to keep all of those mechanical parts running smoothly as they rub against each other. You should always make sure you have enough oil in the motor, and always change the oil filter on the motor as scheduled by the manufacturer.

Cooling

Some electric generators are air-cooled. But a larger generator will often have a cooling system similar to an automobile engine, using a water-and-antifreeze cooling liquid.

If your generator is one of these, you need to check the level of the coolant reservoir regularly, and assure the level is kept within the indicated limits. And, as with an automobile, you need to consider the amount and strength of antifreeze appropriate for the season and region where you are using the generator.

2. The Fuel System

Gasoline Combustion: A Simplistic Explanation

A stand-alone gasoline generator gets its fuel from its own fuel tank. The gasoline is usually fed via gravity to the carburetor on the motor. In the carburetor, the gasoline is mixed with air (or oxygen) and injected into the motor's cylinder where a spark is provided via a spark plug.

This spark causes the mixture to explode, and forces the piston in the cylinder to slide open, which moves the crankshaft of the motor. All of this is done via mechanical timing, which keeps the motor turning.

In a coach with a built-in gasoline generator, the functions are the same, but the gasoline comes from the coach's main fuel tank.

Diesel Combustion: A Simplistic Explanation

A stand-alone diesel generator also gets its fuel from its own fuel tank. The fuel is fed via a fuel injection system directly into the cylinder of the motor, and mixed with oxygen there. Then the piston moves to compress the diesel fuel to the pressure necessary for it to explode.

No spark is needed, nor is there any carburetor on a diesel motor. When the fuel mixture explodes, it forces the piston to move to the open position in the cylinder, thus turning the shaft of the motor. This cycle repeats itself via mechanical timing which keeps the motor turning.

Fuel System Service

These parts of a generator's fuel system will need occasional service:

  1. The fuel filter
  2. The carburetor fuel jets (on a gasoline motor) or diesel fuel injector jets (on a diesel motor)
  3. The spark plugs (on a gasoline motor)

If the fuel filter gets dirty or blocked, even partially, then too little fuel will be provided to your motor, and it may not run. If it runs, it may miss or turn off sporadically.
In a gasoline generator, the spark plug will, over time, need replacement. It can become fouled with carbon or dirt, and eventually the contacts will wear out.

If the fuel jets are blocked, then the motor may not run for lack of fuel. If they are worn, the wrong mixture will be provided, and the motor will not run properly.

You can replace a fuel filter, and maybe even a spark plug if it is placed conveniently for you on the engine, but when it comes to replacing the fuel jets you really want a trained mechanic to deal with that.

3. The Electric Starter Motor

Your generator has to be started by turning the motor until it goes through several firing cycles of several cylinders. Once the motor gets going, the starter is no longer needed, as the motor will run on its own.

The starter motor is electric and requires voltage to turn, and in your coach, this voltage comes from your house batteries. It takes a significant amount of current to turn your generator motor, even more with a larger-sized motor/generator combination.

You should also know that because a diesel motor uses a higher level of compression to force combustion, it is harder to turn, and thus its starter requires significantly more current than a gasoline motor to get it to turn at a high enough speed.

The reason you need to know this is simple. There are some hefty wires coming from your house batteries to the generator of your coach. And you should check occasionally to make sure the following things are true:

  1. Your house batteries are in good shape, and hold a strong charge.
  2. Your connections to your batteries, as well as to your generator are clean, without corrosion, and attached tightly at each end.
  3. When your starter turns, it doesn't make weird sounds, and is actually turning the generator motor's shaft.

4. The Electric Power Generator

Here’s a simple description again, this time of the part of your generator that actually generates the electricity.

Picture a coil of wire wrapped around a shaft. This coil of wire spins inside the opening of a larger outer coil of wire. Visualize that the shaft of your generator is attached to the shaft of the fueled motor and turns when the motor turns.

Leaving all of the electro-mechanics out, if you connect a voltage to the ends of the inner coil of wire, and spin it inside the outer coil of wire, and then attach something like a charger or inverter to the ends of the wires on the fixed outer coil of wire, you will get AC voltage from these output wires.

Again, I have left out all of that complex design stuff like the magnetic metals used, the complex ways that the wires are wound, the contacts used, and on and on. I just want you to know that there are parts in here that sometimes require maintenance.

Luckily, the generator itself is designed for minimal maintenance, and if there is a problem with yours, you need to see a trained generator mechanic.

Useful Reference

Generator Parts That You Can Check and Service

I will now list the things that can and should be serviced periodically. If you want your generator to last for decades, replace the parts below at the intervals suggested by the manufacturer. Running the generator once a month or so is a good idea.

The fuel pump and fuel filter are the parts that most commonly give trouble. Here's an article with pictures on how I replaced a fuel pump and fuel filter in my Onan 5500 generator.

If any of the terms or abbreviations in use here are new to you, check out my article on electrical terms. It might help.

Tips for Generator Maintenance

PartNotes:

Spark plug

With a gas generator, I suggest keeping your old spark plug after you replace it, in case you need one in an emergency.

Fuel filter

Keep a spare, just in case, especially if you use your generator a lot.

Air filter

If the generator is running rough, sometimes you can remove and clean the air filter for better performance, as a temporary solution.

Gas jet

Only a trained mechanic should service this.

Diesel injector

Only a trained mechanic should service this.

Fuel lines

Check for wear or leaks, especially if you smell fuel.

DC and AC wiring

Inspect wiring periodically for wear, torn insulation, and loose connections. If necessary, get a trained mechanic to replace wires.

Motor oil

Check oil level and change as needed, or when suggested by the manufacturer.

Oil filter

These are easy to change. Follow the manufacturer’s instructions.

Coolant

Use the manufacturer’s suggested coolant (anti-freeze) mixture. Monitor the level regularly when using the generator, and keep the level within the limits marked on the reservoir.

Comments Are Welcome

Hopefully, I didn't lose you with my attempt at simplifying how an electric generator functions.

If you experience a problem with your generator, check the comments below for troubleshooting tips, and feel free to post a comment about your own issue!

Basic RV Generator Maintenance

RV Generator Troubleshooting

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: We can't figure out why the roof air in our motorhome isn't working with our 5000 onan generator while traveling. We know there is a 20 and a 30 amp switch on the generator, and then inside the RV, there are two switches by the door; one switch says main battery, and the other is a diff battery. The air works fine while plugged in at camp. We are new to this RV and camping thing, and cannot figure this out. Can you help us resolve this?

Answer: The two switches are called Cut-Off switches and are used to turn OFF your 12-VDC from your Chassis and Coach batteries, so the batteries do not discharge while the RV is in storage.

Your Coach batteries are used to power your power control panel as well as your temperature control panel and other equipment.

So make sure your Coach batteries are fully charged before you check anything else.

I am pretty confident that your main problem is the charge on the Coach batteries.

Question: A red lighting is blinking inside my motorhome generator. What does that mean?

Answer: The ONAN generators utilize this red light and the number of blinks to provide the owner with a few error codes. These error codes should be listed in your generator owner's manual. If not, you can find digital copies of the manual on the web.

Question: I have a 36-foot leprechaun class C RV with no generator looking to buy a gas power generator 1500 watts starting 1200 watts running will that work?

Answer: The first thing to do is check if your Leprechaun has a space designed for a generator? With some models the manufacturer will design a specific cavity (storage area) for a generator as an option.

If this is true with yours then you are lucky in that you will already have the mechanical strength to support a generator, and you may even be able to purchase the wiring etcetera that will make installation easier.

On the other hand, you could be an owner who will use the generator as their external power source and then you only need a modified power cord.

Be aware that a permanent installation will require some special wiring that switched your RV automatically from External power to your generator.

But be aware that your RV is designed to operate on either a 50-Amp or 30-Amp 220-VAC service. I am assuming that the generator you are looking at using is a 10-Amp 120-VAC capability (10Amps of 120-VAC is all a 1200-Watt generator can provide.-- using the formula Amps-Watts divided by Voltage, or 1200 divided by 120 equals 10)

My point is that this will only power half of your 120- VAC appliance and by the way, your Air Conditioner uses 220-VAC, or in other words 2 separate 120-VAC lines.

Question: I have a 1976 Chevy G-30 1 ton Marathon motor home. Where is the generator and the turn-on switch located?

Answer: Not sure of location on a 76 but just go outside and walk around until you see a 1-inch exhaust pipe.

Then follow it to your generator

Question: I'm new to RVing, and I have a brand new motorhome with an onboard gasoline generator. A helpful camper showed me the altitude adjustment when the city power went out in Albuquerque, and the generator would fire, but not stay on. When we got just about to Oklahoma, the generator turned off on me. I went to adjust the setting and discovered the generator cover was gone (that may explain at least one of the weird noises). Could I run the generator without the cover, or will that actually damage it?

Answer: Your generator can operate just fine without the cover. But, you need to get another one from the manufacturer because it is part of the noise baffling system and the noise will not just irritate yourself but your neighboring campers.

FYI: If your new RV has sat for a long period of time the fuel filter for the generator may be partially gummed up from sitting with fuel drying up in it.

I would look under the chassis where the RV generator is mounted, and you should see a fuel pump/filter combination there. Get the model number and purchase a new filter to see if this is why it isn't running properly.

Question: The inside panel of my RV does not have a chocker position for my generator. The outside generator shows off and choke on the same switch. Do I push the off switch on the inside panel for a choke?

Answer: On most generators used in motorhomes, there is no manual choke. It will have an automatic choke.

The switch is actually just an ON - OFF switch that you can hold for a few seconds to get it to start.

That's all I can say about your problem with what you have told me.

Question: My motorhome has a diesel generator. Why does the generator operate off of the house batteries instead of the chassis batteries? It seems to me that weak house batteries will prevent a generator from starting up in extreme heat, forcing the air conditioners to operate. Is there a way to switch the wiring system from house to chassis?

Answer: The philosophy with motorhomes is that you should not have any superfluous appliances loading down your chassis battery. It is definitely not recommended that you "redesign" your RV wiring away from the standard configuration.

The standard system design you have works well, and the power control panel would not operate correctly if you change the high-current wiring.

Question: Our onboard generator starts just fine. I let it run for maybe 5-7 minutes before slipping the 30 amp switch to begin sending power to the appliances etc. They (the coffee maker, microwave), show they are getting power, but then it clicks off. After maybe 30 seconds or a minute, it will look like they are on again, only to click back off again. Do you have any thoughts?

Answer: You didn't tell me what kind or model Rv you have, but most that have a built-in generator has an automatic power sensing system and transfer switch, so I assume you have your 30-Amp Main Breaker turned OFF?

Placing a normal load on your generator should not force it to turn OFF. If your load was too much, then one of your AC-Voltage breakers should have kicked OFF instead. A good generator should operate normally with a load on it.

So, I suggest that you check out your generator as follows; 1-change the fuel filter on the fuel input line, 2- check the electrical connections for any loose wires, 3-If these things seem OK, you should get an electrician to service the generator for you and find the problem.

Question: Can I run the generator on my RV to power an appliance, such as a toaster oven, while I am driving?

Answer: Yes, of course. Your generator will provide power to ALL of your electrical devices when not plugged into external power including a toaster and even your roof AC.

Question: What might cause a new generator in a new camper to turn on, but only run for a minute or so?

Answer: The top two problems with generators in RV's is the fact that they sit for a long time and the fuel filter and the fuel pump both get gummed up.

So, check the filter and fuel pump. They are an assembly mounted under the chassis under the generator, and they're relatively easy to change.

There is also a little secret about generators on RV's. Long ago, many people would go out into the Boondocks and run all of their gas from the RV tank and then not be able to get back to civilization. So, Rv manufacturers would only run the fuel line for the generator 3/4 of the way down into the RV fuel tank. That way the RV owner always had enough gas to get out of the Boondocks. Check that your RV fuel level is above 1/4 tank.

Question: Why does my new generator in my RV not power anything? We have full power when plugged into electricity.

Answer: From our symptoms, I have to assume you have a motorhome with a built-in generator?

If this is the case then I also have to assume that the generator runs but your Rv does not switch over to it for 110-VAC power?

With these two conditions being true, then you should know that your motorhome has a "transfer switch' which is actually a solenoid that your power management panel used to select either the external power or the generator for power. Two AC power sources cannot be tied together so this transfer switch doe the job for you. When the power control panel senses that the generator is running and generating power, then it switches over to the generator as long as it is running.

So, check two things first;

1- is your Coach battery fully charged? If not, your Power Control panel will not operate properly. If the battery is OK, then you may either have a bad "power generator" portion of your generator, or

2- you could have a bad transfer switch. The transfer switch being bad is the most common cause of your problem.

Question: Our R.V. Generac generator has been working fine, but now it will not even turn over; no click, nothing. What can we check to get it working?

Answer: Your generator gets its power for starting and for its fuel pump from the Coach 12-VDC batteries. So, of course, check that you have power from the batteries and that they are being charged by your Converter (which get's its power from the 110-VAC system.

If you put a multimeter across your battery terminals, it should read around 13.5 VDC if charged and around 14.5 VDC if it is being charged.

I suspect that this is your problem, but if the generator still does not start, or even "click" you will need to trace your 12-VDC to make sure it is present on the generator starter terminals themselves, and they are a little hard to get to.

Question: does the generator connect directly to the coach battery or to the converter?

Answer: When your generator is turned ON, it replaces your External power source so the internal wiring of the RV is no different.

And, the Coach battery is kept charged by your Converter which operates on your RVs 110-VAC electrical system regardless of which system (External or Generator) is your AC-Power source.

Question: The power in the campground went out. Do I have to turn the electrical breaker switch off before starting the generator?

Answer: An RV with a built-in generator will automatically switch over to the generator when you start it, and back to shore power when it is turned off. This is a safety feature in motorhomes.

Question: I just bought a trailer and the AC, microwave, etc. won’t turn on when the trailer is on. I am a newbie. Am I missing something?

Answer: If you're plugged into a campsite power box, then check the following;

1- Did you turn the power box breakers to ON?

2- Is your power cord firmly plugged into the power box and your camper?

3- Is your trailer's MAIN power breaker turned to ON?

These are the three essentials a newbie might not check.

Question: My Generac seized up, so I'm shopping used Onans. Do you think I need to buy the Onan install kit to put it in?

Answer: I would recommend that you get the install kit. Otherwise, if you have problems in the future, you will probably suspect your custom wiring as your culprit when things go wrong.

Question: I have a diesel 8000 Onan pretty new coach 2017. Had issues on my last trip with the transfer switch which I got replaced. Just took a short trip and the generator keeps shutting off when I am driving. I had to turn it on several times, runs for a while then shuts off. What is odd is that when I got home I had it on for about an hour with both A/C’s on with no problems. Took a 15 min trip to sprays and it went off again. Do you think it could be the batteries? Oil level is good.

Answer: There is a safety feature designed into motorhomes that some people don't realize.

The motorhome manufacturers place the fuel line for the generator only down to the 1/4 tank mark. This restricts the driver from using up all of the engine's fuel while out Boondocking, and then not be able to get to a place for a refill.

So, first, you should check that you have enough fuel in your tank to run your generator and also drive.

If this is not your problem then you might want to change the fuel filter for your generator.

Question: Can I start my onboard generator without my RV running?

Answer: Yes, The onboard generator starts using your COACH battery. And, when it is running, the external power is switched OFF.

And it is common for some motorhome owners to run their roof air conditioners and some other equipment while they are driving on the highway.

Question: why are our RV's TV and refrigerator not working when we are plugged into the electricity?

Answer: Without knowing what design RV you own, I can only guess at which systems yours uses.

So, Your TV's typically use receptacles that are powered by your INVERTER, so they will operate when you are Boondocking and don't have external electrical power. So check that the Inverter is operating.

2- Considering that your Inverter operates on your COACH battery, you should check that it is operating properly.

3- Your fridge should operate on 110-VAC when your RV is plugged into external power, BUT the fridge control circuit board operates on your COACh battery.

I would suggest that you check your Coach battery and that it is being charged properly by the RV Converter.

Question: I have a 2003 Itasca MH other 50 amp service. It has an onboard generator that works fine. Can I wire in a 220-volt outlet from the fuse panel to run a 220-volt clothes dryer?

Answer: Here are several things to check:

1. Most RV's are pre-wired and plumbed for a washer/dryer hookup. Check if yours is prewired

2. Your generator should typically be a 5K generator, and this would be enough power capacity for your washer/dryer.

3. You would need to add the appropriate breakers for a washer and a dryer.

4. Most RV's use a combination washer and dryer unit to save space, but I have seen some RV's where separate units were added.

5. Remember these appliances are heave and MUST be mounted so they will not bounce around and damage your RV's interior.

So, considering the things I have listed here, yes, you can add a Dryer hookup but make sure to do it safely.

Question: Our generator is on but our microwave is not getting power. How can we connect the microwave to our RV's generator?

Answer: Your microwave, your AC units, your 110-VAC receptacles your Fridge, Ice-maker all operate on your external campsite external power normally. When you start your generator, your Power Control panel senses that it is ON and it switches your power over to the generator.

If the generator is running then you should check that your COACH batteries are fully charged and your CUT-OFF switch is ON.

If these conditions are met, then your Power Control panel should switch over to the generator, IF the battery is dead or has a very low charge then the Power Control panel will not operate properly.

Question: If I have no appliance battery in the RV but the ground for the circuit is plugged in; will it kill the vehicle?

Answer: Not a lot of information, but here goes;

1- What you call the appliance battery is normally referred to as the COACH battery. It is used only for the camper trailer or motorhome 12-VDC accessories and appliances.

2- The COACH battery on a motorhome (which I am guessing you are talking about) is not a part of the "vehicle" electrical system.

At the same time, if you have not been using your CUT-OFF switch to disconnect the engine battery when the motorhome is not in use, the electrical devices that operate on your engine battery, even when OFF will drain your engine battery.

Question: I have a 96 class a motorhome. I am new to roving there is black soot on the generator I took it to a nearby shop and had the generator exhaust pipe rehang with a new hanger. Do you think the black soot could have come from exhaust pipe being separated from the generator?

Answer: Back in the day before automobiles were computerized, it was common knowledge that 1- if your gasoline engine smoked and it was blue, then you were burning oil, and 2- if your engine smoked and it was black, it was "burning" gas.

Ans, if your generator exhaust was disconnected then, yes, the exhaust could be getting inside the generator housing.

Check the total hours on the generator before you start to get an indication that it may just be worn out or not and need replacement or an overhaul.

If it were me, I would have the generator 1-steam cleaned properly, 2- install new air filters, 3- change the engine oil, 4-install new fuel pump filter, and then have it "tuned up" by a generator mechanic.

The mechanic will be able to tell you if the generator can be fixed or not.

Question: My RV onboard generator sometimes powers up the coach (microwaves/outlets) and sometimes it doesn't. It starts with no problem and transfer switch is fully functional and new. What could be the problem?

Answer: From what you have told me here, your generator is functioning and running properly but you do not have any AC power in your RV, at times.

If this is the case then you need to have a tech check out the "power generating" portion of your Generator. It sounds like there might be a problem there, or you could have a loose wiring from the generator to the RV power system.

Question: I have a 1997 Allegro Class A. When I turn the ignition switch to off the generator shuts off. What do I do to keep it running without the ignition switch on?

Answer: The generator does not use the engine power, and the ignition switch should not have any effect on its operation. So, I would check that the MAIN and AUX (12-VDC) switches are turned ON so that the generator can have 12-VDC to start and run. Otherwise, there is no reason for this to happen.

Question: I am new to using my generator to power my RV. If there is no shore power, do I plug the electric cord in the outside compartment into the receptacle in the same compartment? What is the outside receptacle for?

Answer: You should have an External Power cord that fits into the External Power Socket on the outside left rear of your RV. It is a special waterproof cable that is capable of handling either 30-Amp or 50-AMP power which is why it has the "strange-looking" connectors on each end.

Question: I have a 2006 Conquest SE with an onboard generator. The generator starts and runs, but it does not seem to run anything. Is there a switch or something to make the appliances work?

Answer: Your microwave, your AC units, your 110-VAC receptacles, your Fridge, and Ice-maker all operate on your external campsite external power normally. When you start your generator, your Power Control panel senses that it is ON and it switches your power over to the generator.

If the generator is running, then you should check that your COACH batteries are fully charged and your CUT-OFF switch is ON.

If these conditions are met, then your Power Control panel should switch over to the generator, IF the battery is dead or has a very low charge, then the Power Control panel will not operate properly.

Check the battery.

Question: will a 3,000-watt generator operate the A/C while parked?

Answer: The built-in generator of motorhomes, if it is a 3K or a 5k, are typically designed to provide adequate power for all of the internal 110-VAC equipment and accessories. Sometimes, the user can have too many appliances plugged into the RV receptacles and cause the main or one of the receptacle breakers to kick out.

Question: Our heater just stopped working. We just got this RV and drove it twice. It says the propane is full. It’s a 2015 Thor Axis 24.2. Any advice?

Answer: First of all, make sure your valve for the propane line is turned to "ON".

Then, check that your propane is working by turning on one of your stove burners.

Once these checks are run, then check that your COACH battery is fully charged because it's 12-VDC powers your temperature control panel.

Check if the temperature panel is operating by turning on your AC.

If everything operates OK, then your furnace itself is the likely culprit and needs to be checked by an RV tech.

Question: How many batteries are there in a 1985 Ford Tioga RV?

Answer: I don't have any specs on an RV that old (1985) but, typically these older Class-C motorhomes will have an engine battery and it will have another 12-VDC battery for the interior accessories and other equipment that operates on 12-VDC.

Having such a second battery takes any load and current draw off of the engine battery, so the Rv is always ready to start and go.

Question: We just bought a new, never used Holiday Rambler Diesel Navigator 38F. The generator is a Cummins, and it won’t turn on, it just ticks. The batteries are brand new and show that the voltage is good, and I have the motorhome plugged into our home. Can you tell me what is wrong?

Answer: Your generator starter is powered by your coach batteries.

Make sure your Cut-Off switch is in the right position to allow power to the interior equipment, and make sure the batteries are fully charged.

Also, make sure the batteries have water in them.

If you just hear a clicking sound and the generator is not turning, then your battery voltage is most likely your problem.

Question: Does the Onan RV generator make its own power to run? It's in a 1998 Coachmen Catalina Class C Motorhome.

Answer: The Onan generator in any motorhome uses the COACH battery to start and then it actually operates on the RV's fuel system.

Question: What kind of oil do I put in my RV generator?

Answer: Read the generator owner's manual and it will list the acceptable products to use. Typically the recommended oils for most generators are similar to auto engine oils, but I would check what is recommended for my specific brand and model.

Question: Why would a carburetor be a problem on a brand new Class C RV? The dealer is refusing to fix it under extended warranty, and blames us for not using it enough.

Answer: First of all, a warranty is a warranty and they typically only have an end date or mileage limit. And I suspect that if you read yours, it will not say anything about how much you use your RV.

Most newer RV's will utilize a fuel injection system rather than an old-fashioned carburetor, but whichever you have the Rv will have at least one fuel filter.

These fuel filters are what will "gum-up" if they sit and the engine is not run regularly. Most people will run their Rv engine for 20 minutes or so every month just to avoid this kind of problem. So I would MAKE the dealer check the fuel filter.

But if it is gummed up, that would be an expense of yours. As it is an expendable part.

Question: I have a 1999 Coachman Class A with an Onan 7000. My problem is that the generator will not change the coach batteries. Any thoughts?

Answer: Your motorhome has a Converter that charges your COACH batteries, and it is powered by your 110-VAC regardless of whether you are running on your external power or your generator.

Check that you do have power out of the generator to other 110-VAC appliances and that all of your breakers are reset.

Question: I changed the oil and filter on the generator in my motor coach and now the generator won’t start what could be the problem? It is a 33 0 diesel.

Answer: Changing the Oil/Filter on an RV's generator should not have any effect on it operating unless your oil level is low.

Many generators will have a sensor that detects if the oil level gets low and stops the generator from running to protect it from damage.

But, if you have adequate oil in the generator, this shouldn't be the problem.

So, check your oil level.

Question: I have a 1976 Chevy G-30 1-ton Marathon motorhome. Where are the generator and the turn-on switch located?

Answer: The simplest way to find your generator is to look for the 1-inch diameter exhaust pipe and trace back to the generator itself.

There will be an On/Off/Start switch on the dash of your motorhome and on the generator itself.

Question: My RV generator is running, but only the microwave is powering up! What do you think is the problem?

Answer: First of all, is your COACH shut-off switch turned ON? It runs on 110-VAC like the microwave.

Secondly, is your converter (charger) keeping your COACH batteries charged? Check the voltage on the terminals of the Coach batteries.

Question: A few minutes after turning on our Onan Generator on our class C rig, it smelled like it was burning. What do you think the problem could be?

Answer: Pull the covers off of the generator and inspect it for road debris. Then, examine the generator exhaust pipe for road debris. If everything is OK, then you need to get that generator to a service center.

Question: I have 2004 Fleetwood Discovery with a diesel 7500 generator. While running it shows 13 amps being used but the only device on is the fridge. Not sure what else is making the amp draw. Can you help?

Answer: Your converter would be running and keeping your 12-VDC COACH batteries charged. So, are these batteries in good condition and do they have water in them? Many motorhome owners will forget to maintain their batteries.

This is also a common problem on motorhomes which have batteries that have aged. I recommend that you check this first.

Question: My generator won't turn over, I just installed 2 new coach batteries. The breaker for the inverter/ converter won't reset. I was wondering if this non-resetting breaker could be a problem when trying to start the generator?

Answer: Some companies do make a unit that is a combination Inverter and Converter, but this is not common and they are separate units.

Neither the Inverter or Converter are used to start your RVs generator. The COACH batteries are used for starting your generator. So, it sounds like you have two problems.

I suggest that you go back and recheck the wiring to your COACH batteries and make sure you have everything wired properly. Your Converter is used to keep your COACH batteries charged and your Inverter will use your 12-VDC from your COACH batteries to power a few receptacles that you use for your TVs and maybe for a computer while you are traveling.

Considering all of this, your symptoms suggest that you have not rewired the new batteries properly, so again, make sure that you have things hooked up properly.

Question: Can you run an Onan generator with the engine off?

Answer: Yes, you can run your motorhome's generator when the engine is OFF.

Your Electrical system in your RV is designed for your generator to support all of your electrical equipment while you are camping at a site where there is no electrical hookup.

Question: I have an RV bus with an onan 7500 gen. The generator starts and runs all of the coach except a/c units. When I turn either a/c unit on the front or back it shuts the gen down in about 5 min. Gen repair shop are telling me my coach batteries are bad. Will that make gen shut down when a/c are turned in?

Answer: If your Coach batteries are not holding a charge then the temperature control panel will lose its 12-VDC power and shut down your AC units. This would happen when your AC units cycled.

I assume the generator repair shop measured your 12-VDC and noticed a sag in the voltage after a while. Check your batteries; 1- how old are they? 2-do they have water in them?

Question: I need to wire up my shore power and generator power for my outlets and air conditioner to work. In the generator outlet box, I have the generator plug wired in and it is receiving 122 volts. There are two additional sets of wires coming from the top of the mental outlet box (two orange wires = 6 wires). How do I connect these wires to the generator plug in order for the coach and shore power to get power from the generator?

Answer: First of all, your AC units in your RV operate on 220-VAC. Your external power cable uses 4-wires; two are separate 110-VAC sources, one is your COMMON wire and one is your GROUND wire.

Without any more information on your situation, that's pretty much all I can tell you.

BUT ---- Make sure your generator is capable of generating two different 110-VAC outputs, and then make sure that you wire the COMMON to COMMON and the GROUND to GROUND and you don't mix things up.

AND, I m assuming you have an RV that is already wired with a TRANSFER Switch system that will select between the Shore and Gen power systems? They must be kept isolated from each other with this kind if Power Transfer switch.

Question: why do the gfci plugs only work when the converter is turned off when using our generator?

Answer: Your GFCI receptacles get their 110-VAC from the MASTER GFCI receptacle. It, in turn, gets its 110-VAC from your AC-Power breaker panel, just like all of your other 110-VAC receptacles do.

Your Converter is simply a charger, plugged into a receptacle, that keeps your COACH battery charged.

Your RV normally gets its power from the external power cord or from the generator and this is sensed and switched using the input Transfer switch.

The AC Power breaker box does not power the Converter separately.

But, if your COACH battery is BAD then the battery will not be charged, and many of your 12-VDC devices in your RV will not operate properly, such as; interior lights, temperature control panel, power management control panel, alarms, and more.

But, there is no connection between the Converter and the GFCI receptacle!

Question: We have a 2017 Thor Chateau 24. On a trip, a pipe hanging underneath the RV that exits near the driver’s door dropped down. It elbowed up toward the engine. I removed the hangers and the pipe. The engine light was also on prior to me finding the pipe problem. Is this a generator exhaust or something else?

Answer: A generator exhaust pipe is typically a 1-inch diameter pipe while the engine exhaust would be much larger, so let's assume the pipe goes to your generator.

Other than that, your engine light being on can be an indicator of something simple most of the time. But, you need to get that checked as soon as possible.

Question: Does a Onan Microquiet 4000 have a fuel filter?

Answer: Yes, the normal configuration of an Onan generator in an RV is to always have a fuel filter on the input fuel line. They are often configured with the fuel filter screwed onto the end of the external fuel pump.

Question: What's your opinion about propane generators?

Answer: Well, As they say; opinions are worth what you pay for them, and mine are free! LOL!

Anyway, the new designs of generators whether they run on gas, diesel or propane work fine. So, it comes down to your personal application and which fuel you want to use.

For instance, If I had a Gas or Diesel RV then I would use a generator that uses the same fuel; strictly for convenience sake. And honestly, a propane generator should be just as good for you.

Question: The alarm for carbon monoxide beeps its warning a few minutes after I started the generator. Doesn't matter if I have a table fan blowing at the alarm, nothing helps but shutting it off and waiting 15-25 minutes for the alarm warning signal to stop. I've not driven with the generator running yet, so I don't know if it'll happen in motion too. Is the exhaust directed away or released below my coach?

Answer: Your RV generator exhausts under the edge of the RV, but you should not have any of this getting into your RV!!!! I would suspect that your problem is something else. For instance, you could possibly have a bad alarm, or you could be getting CO from your gas furnace or range or gas oven. In fact, it is not uncommon for the propane lines to loosen over time in RVs from the movement when traveling.

Question: In the house battery tray there are two red cables that look like one from the generator and one from the converter/battery charger and then one black cable but all the videos show only one red and one black so should I put the two positives on the positive post together or how should I hook up the batteries?

Answer: With only the information you have given me, I can only assume you have a motorhome that was factory wired with a generator in it.

With this being the case, normally, you would have a wire from the Converter that would connect to the battery PLUS terminal and keep the battery charged when you are operating on Shore AC-Voltage.

There should also be a wire from the House battery that provides power to start the generator.

And there is often another wire connected to your battery that powers your INVERTER.

You will have to trace the wires to determine which is which.

© 2010 Don Bobbitt

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