Troubleshooting and Maintaining Your RV’s Air Conditioner

Updated on December 14, 2017
Randy Godwin profile image

Randy is a lifelong lover of the outdoors and especially camping. This article is intended to help the RVer save money and time on repairs.

A new Coleman 13,500 BTU A/C unit ready to install.
A new Coleman 13,500 BTU A/C unit ready to install. | Source

The rooftop air conditioners used on motorhomes are made to give many years of dependable cooling efficiency, especially if you maintain them.

This article has two parts: first, how to troubleshoot your AC and decide which parts to replace or service; and second, how to maintain your AC.

These repair and maintenance tips are very simple to follow, even for those without much hands-on experience.

Part 1: Troubleshooting

Some Background: How Your AC Works

If you are unfamiliar with how a motorhome air conditioning system works, this companion article will help you understand which parts of the motorhome rooftop air conditioner unit to check, service, and repair.

Briefly, your air conditioner, which may be combined with a heating system, includes a compressor—to circulate a cooling fluid like Freon through the coils and fins of the condenser—and a fan, to blow cooled air through the RV. The fan and compressor are turned on and off by a thermostat—a switch attached to a thermometer—and kick-started by one or more capacitors. The thermostat and other controls are run by the vehicle's 12-volt electrical system.

Where to Start Investigating

Many problems your air conditioner might have—sluggish behavior, turning off prematurely--can be resolved by checking out the electrical system in order, going first through the possibilities that are easiest to resolve. These easier choices often solve the problem. If they don't, you can investigate further so you can decide if you need to replace the big items like the fan and the compressor or get a whole new AC unit.

First, we'll address the common electrical issues.

A Precaution

Before attempting any maintenance or repairs on the rooftop AC unit, be sure to switch off the electrical supply to the unit, either by tripping the breaker or by unplugging the motorhome from the electrical receptacle.

RV AC Issues You Can Troubleshoot Yourself

  • If your AC does nothing and makes no noise, make sure your unit and its controls are getting power.
  • If your AC fan or compressor is slow to start, doesn't blow any air, blows weakly, blows only warm air, stops after a while, dims your lights, or trips your breaker, you should first check your capacitors and replace them if needed. 

  • If there's no air blowing, check the fan capacitor; if there's no cooling, check the compressor capacitor.
  • If the capacitor is okay, you should look at whether the thermostat is getting power by checking whether the 12-volt appliaces work.
  • You can check the function of the thermostat if it's wall-mounted. If the unit only works when thermostat wires are touching, the thermostat is bad. The thermostat is easy to replace.

  • If the capacitor and thermostat are okay, the control board may be bad.
  • If the control board is okay, you may have to replace the fan motor or the compressor.

  • If the fan only works at certain speeds, the fan motor may be bad.
  • You can have the fan motor rebuilt (if it's not the sleeved-bearing type). Or you can replace the fan motor yourself if the unit is in good shape otherwise.
  • If the compressor is bad, it should probably be replaced, not fixed.
  • If your system drips or overheats, the coils may need cleaning.
  • If the roof AC leaks, the bolts may be loose or the gasket may be leaking.
  • If the system is very cold or ice builds up, it may be low on Freon.
  • If the unit is noisy, something out of place may be interfering with its motors; you can check by removing the shroud.

The First Step: Is There Power?

If your unit does not react at all—does not go on and does not make noise—you will want to make sure it is getting power. Look in the 12-volt panel and check that the fuse has not blown or the breaker has not tripped. The 12-volt power system runs the controls to the AC including the thermostat.

Running the AC unit itself draws a lot of higher-voltage power, maybe too much for a 15-amp power pole, and if there are two modern rooftop units they may draw too much for the 30-amp power supply provided at many campgrounds. If the unit draws more than the system can provide, the breaker or fuse will shut off. Fortunately, many campgrounds and RV parks now provide 50-amp service for modern multi-unit AC systems.

The thermostat is run by 12-volt power, like your motor home's lights and vent fans. If these accessories aren't working either, there is something wrong with the 12-volt power. A breaker may be bad or there may be a loose connection in the breaker box. Occasionally the power converter that converts your higher-voltage power to 12-volt power is bad.

Next: Consider the Capacitors

If the fan or the compressor fail to start, it is possible the starting capacitor is malfunctioning. A bad capacitor can cause a variety of symptoms: the AC unit merely hums and "tries" to start, it runs a few minutes then trips a breaker, the fan won't start without a push, or it blows only hot air because the compressor can't start.

The capacitor stores electricity to give both the fan motor and the compressor an extra boost whenever the RV AC unit starts. It is not unusual for the capacitor to go bad, especially if the RV sits unused for a while, and not be able to provide that little push that gets the motors going. On occasion a bad capacitor will explode with a puff of smoke without damaging the rest of the unit.

There may be one capacitor for both compressor and fan, two capacitors (one for each part), or even three or more all together. A capacitor is often shaped like a small battery, flask, or button.

If you have a multimeter in your tool kit, you can use it to test the capacitor. A good capacitor should show a random value on the multimeter that slowly decreases the longer you keep the probes in place.

A bad capacitor is easy to replace. Check the required voltage and model numbers on the old capacitor when ordering a new one.

When replacing it, make sure the power is off. Observe which wires go into it where, and make a note so you can install the new one exactly the same way. Don't touch its terminals with your bare hands. Before you throw the old capacitor away, drain out its electrical charge by connecting its terminals with a screwdriver (make sure the screwdriver handle you are holding is insulated).

Very often, your AC unit will start and run fine after you replace a capacitor.

A capacitor.  Often a cylindrical container, but yours may differ.
A capacitor. Often a cylindrical container, but yours may differ. | Source

Next: Check the Thermostat and Switches

A bad thermostat is another possibility. If you have a wall-mounted thermostat, you can check it by checking its voltage with your multimeter. If the unit only goes on when you touch the thermostat wires to each other, the thermostat is definitely bad.

If the thermostat and capacitors are all okay but the AC still doesn't work, you may have a bad control board.

Thermostats and switches may be purchased online by finding the correct model and serial numbers before ordering the new parts. These items are easy to replace in most cases. As always, make note of and remember the wiring connections when replacing these electrical components.

Is Your Fan or Your Compressor Bad?

If after you check these electrical items your AC still doesn't blow out air, or it blows only at certain speeds, your fan motor may be bad. If your AC blows but only hot air comes out, your compressor may be bad. Sometimes—not necessarily—a fan or compressor smokes or leaks oil when it goes bad.

A compressor that is working should turn on audibly and feel warm to the touch. You can test a compressor with a clamp-on ammeter, if you can rent or borrow one. Check how many amps the compressor is drawing. If it draws much more current than the amp rating written on the unit or on a nearby plate, the compressor is toast.

You May Be Able to Rebuild or Replace Your Fan Motor

Oiling your fan motor, as shown in Part 2 of this article below, will help it run more easily. If your AC fan motor is slow to start even after oiling, or needs a nudge to get it going, or only runs at certain speeds, or doesn't run at all, it will need to be rebuilt or replaced.

Fan motors come in two types: with exposed bearings which may be lubricated easily or with sleeved bearings (see the last photo in the article). The first type of fan motor may be rebuilt fairly cheaply and will last for many more years. But not so a sleeved-bearing AC fan motor.

Unlike fan motors with bearings, a fan motor with sleeves cannot be rebuilt economically, and must be replaced with a new one if it goes bad.

If your AC unit seems to be in pretty good shape otherwise, you can order a new AC fan motor to fit your particular unit. There are many sizes and models to choose from. Check the numbers on your old motor. By looking at pictures and descriptions on Amazon you may be able to identify a universal motor that will fit your unit.

Replacement of the AC fan motor is a simple job requiring only a few tools. If the electrical connection to the motor isnt a simple plug-in, mark down the colors of the wires before removing the old fan motor.

Test the new fan motor, before replacing the AC shroud, to check for proper alignment and fan clearance.

Removing and Replacing the Fan Motor

RV AC fan motor with retaining screws removed from AC chassis.  Your RV AC model may be different.
RV AC fan motor with retaining screws removed from AC chassis. Your RV AC model may be different.
Model and serial numbers on RV AC fan motor
Model and serial numbers on RV AC fan motor

A Bad Compressor Isn't Usually Worth Fixing

Compressor
Compressor

If, after you determine that the switches, capacitor, and relays are not at fault, the RV AC compressor fails to operate correctly and cool your air, it is usually better to just junk the unit and buy a new one.

Unless you have access to a used compressor and have the means to replace it and recharge the system yourself, it will likely be too expensive a repair. Under normal circumstances a compressor will last much longer than its warranty.

It May Be Simpler to Replace the Whole AC

If after investigating these possibilities you decide your old RV AC unit has enough problems to need replacing, please see my article on how to install a new rooftop RV AC unit. Replacing your old unit with a more efficient RV AC unit is a very simple and quick procedure you can do yourself.

Some Miscellaneous AC Problems and What May Cause Them

If your AC does run, but only with problems—overheating, dripping, being way too cold—you can address these problems too.

  • Overheating may be due to a simple failure to clean the coils—something I show you how to do in the second half of this article. When the coils are clean they can disperse excess heat into the air.
  • If water leaks into your unit and seems to come from the AC, investigate to see where it is coming from. The leak may come from the gasket between the unit and the roof; if so, it's easy to address. Tighten the bolts carefully, and if that doesn't work, replace the gasket.
  • Dripping from the unit itself may be caused by water condensing in the wrong place (in the pan under the air conditioner) instead of being evaporated by the fan. Such water buildup may be due to dirty coils, and if so, you can cure it by cleaning the coils.
  • If your unit blows very cold and builds up ice—and especially if it later stops cooling at all—it may be low on Freon. Sometimes you can see a visible oily residue around a Freon leak. You may be able to add Freon to your system yourself with a self-piercing valve.
  • If your motor is noisy, you can investigate the problem by taking the shroud (the cover) off the roof AC unit and seeing if everything is in place. The rubber shock absorbers on the compressor and fan may be interfering with the motion of the unit.

Part 2: Maintenance

Accessing the Condenser and Evaporator Coils to Clean Them

Removing the RV AC shroud retaining bolts
Removing the RV AC shroud retaining bolts

Maintenance gives your AC longer life and better efficiency. Roof air conditioning units on motorhomes are the same as ones used on other types of RV campers such as travel trailers and pop-up campers. These repair and maintenance procedures are identical for all these types of campers.

After a few seasons of use, it isn’t unusual for the AC unit to not cool the motorhome as quickly or as efficiently as it once did. Even if you clean the filters regularly, the evaporator and condenser coils will eventually become coated with dirt and grime, which inhibits airflow and cooling efficiency.

Before attempting any maintenance or repairs on the rooftop AC unit, be sure to switch off the electrical supply to the unit, either by tripping the breaker or by unplugging the motorhome from the electrical receptacle. You are now ready to remove the RV AC shroud (above) by unscrewing the four bolts securing it to the RV AC unit itself.

How To Clean the RV AC Coils

This coil is badly in need of cleaning
This coil is badly in need of cleaning
These coils are badly in need of cleaning too.
These coils are badly in need of cleaning too. | Source

After removing the AC shroud you will be able to see the evaporator and condenser coils on either end of the RV AC unit.

If they appear similar to those in the photos above then they need a thorough cleaning to allow unrestricted airflow through them.

Although regular household cleaners may clean the coils to a certain extent, AC coil cleaners made especially for the purpose, like ZEP Foaming Coil Cleaner, will remove the grime build-up much more efficiently and will not harm the coils themselves.

Follow the instructions carefully for the best results. A good wet/dry Shop Vac will help you clean up afterward and remove any excess cleaner or grime from the RV AC unit.

Use a coil fin comb to straighten any bent fins because they too will keep the airflow from moving through the AC coils efficiently.

These fin combs are very inexpensive and may be used many times in the future on both RV and home AC coil fins.

Air Conditioner Fin Comb
Air Conditioner Fin Comb

Straighten out those bent coil fins and increase the efficiency of your A/C unit.

 

Maintaining the AC Fan Motor

RV AC fan motor with a sleeved bearing.
RV AC fan motor with a sleeved bearing.

While the RV AC shroud is removed, it is a good time to service the fan motor and clean the fan itself. Whether your RV AC unit is made by Coleman, Carrier, Duotherm, or Dometic, it will have one fan motor which turns both the squirrel-cage fan and the heat exhausting fan.

This motor should be oiled at this time.

If your RV AC fan motor has regular bearings, there will be oiling ports at each end of the motor. It may be necessary to remove the metal sheeting over the top of the fan motor, plus a few sheet metal screws, to access the bearing oiling ports.

If no oil ports are evident, then your motor has sleeves instead of bearings. You may still oil the shaft at the point where the sleeves enter the fan motor housing. The oil will seep inside and help the fan motor last much longer.

Covering Your Motorhome AC Unit in the Off-Season

Your motorhome AC unit should give you many seasons of dependable operation if serviced annually. It's good to put a cover over the AC unit during the times when the motorhome is not in use.

These inexpensive RV AC covers protect the unit from moisture, extreme cold or hot temperatures, and debris from storms, birds, and insects. They will more than pay for their cost over time.

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    • profile image

      Dawn 5 hours ago

      My Dometic rooftop ac will sometimes just hum, then eventually start. I have had the capacitor replaced, and had it checked again, and it's good. When it is humming, I can reach up and spin the fan freely, but it doesn't force it to start. There are no critters or obstructions. I have replaced the thermostat.

      It seems to happen when I haven't used the ac for a while. I have had a mobile tech out, and of course it started working when he got here, and he couldn't find anything wrong.

    • Randy Godwin profile image
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      Randy Godwin 4 days ago from Southern Georgia

      Hey Shannon, I once had different shrouds for sale on this page but the site removed them for some odd reason. You can find replacements on Amazon or perhaps a used one could be found at the local auto salvage yards.

      Clean the coils well with a good no-rinse spray foaming coil cleaner and have the capacitor(s) checked and replaced if necessary. Good Luck!

      Randy

    • profile image

      Shannon 4 days ago

      I just recently purchased an older small living quarters trailer. I need to buy a new shroud for it, because the venting slats ( if that makes sense) are taped together...not super attractive. On the inside switch, there it says COLEMAN MACH, no number. How do I know what model it is and what shroud would cover it? It's been sitting for awhile at the dealership and the a/c hasn't been used. Any tips to get it in great shape before I use it a lot this summer? Thanks!

    • Randy Godwin profile image
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      Randy Godwin 2 weeks ago from Southern Georgia

      Check the capacitors first, Ken.

      Randy

    • profile image

      ken 2 weeks ago

      Hi my roof top ac unit comes on and runs cold but never stays on long enough to cool the entire camper

    • Randy Godwin profile image
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      Randy Godwin 3 weeks ago from Southern Georgia

      Dan, have the capacitors checked and replaced if bad. This should tell you something!

      Randy

    • profile image

      Dan 3 weeks ago

      Hi

      Looking for troubleshooting suggestions as our 4700 Coleman Mach air conditioner has just stopped working, it was in auto function mode when it stopped. The unit/caravan is only 2.5 years old. It doesn’t have its own circuit breaker and there is power to my caravan

    • Randy Godwin profile image
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      Randy Godwin 3 weeks ago from Southern Georgia

      Autohaus, the problem is either the thermostat or the control board.

      Randy

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      autohaus 3 weeks ago

      great article, very helpful,but my problem is not listed. My ac wont shut off and it is in the auto mode, I have to through the breaker to shut it down,and the same to turn it on

    • Randy Godwin profile image
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      Randy Godwin 6 weeks ago from Southern Georgia

      Samaya, there's obviously some sort of vibration causing the problem. It may be in the motor itself. Sorry, that's all I have without seeing the unit myself.

      Randy

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      Samaya 6 weeks ago

      I have a 2014 Airxcel roof top unit on a 2014 5th wheel. The plastic squirrel cage keeps breaking. Everything in the AC looks fine, the axel coming off the motor doesn't appear bent, nothing is 'hitting' when the AC runs - but the cage broke Oct 2015, Jan 2017 and then again Oct 2017. In Oct, they removed the unit and resocked it down to be sure it wasn't off center. Even so, that cage didn't last even 24 hours so they replaced the cage again this time with a metal one and the unit works fine, but it's loud. The metal cage 'whistles' and is too noisy for nightime (sleep) usage. That isn't acceptable in the summertime in FL, (where I live). The RV Repair place has given up. I don't know what else to do. Any thoughts?

    • Randy Godwin profile image
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      Randy Godwin 6 weeks ago from Southern Georgia

      Tom, either rent or borrow an amp meter to check the compressor. I don't know of anything else which will cause this problem unless there's a bad short somewhere.

      Randy

    • profile image

      Tom 6 weeks ago

      The old start capacitor smoke before it when up also. I don't know what would cause this problem I had it plug into house 20 amp breaker and that did not trip

    • Randy Godwin profile image
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      Randy Godwin 7 weeks ago from Southern Georgia

      Tom, it's not rare for a cap to be bad even if new. Did the compressor seem to draw more amps than normal?

      Randy

    • profile image

      Tom 7 weeks ago

      A/C did not work, change all capacitors Turned a/c on started fine and was running almost a minute then a noise and smoke blow out the top of the start capacitor. All wires hook up the same way??

    • Randy Godwin profile image
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      Randy Godwin 2 months ago from Southern Georgia

      Hey Russell, more than likely its a bad capacitor. Any local AC or electric motor repair service can test them for you. A relatively inexpensive and easy fix.

      Randy

    • Randy Godwin profile image
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      Randy Godwin 2 months ago from Southern Georgia

      PrarieFire, if the compressor is coming on then the AC should work unless the Freon is low. The residue on the tubing could be a sign of a slow leak.

      Randy

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      Russell T57 2 months ago

      Hi Randy

      I have a Coleman Mach ducted ac and today it stopped cooling.

      The fan runs but the compressor does not try to come on at all. It is cool to the touch. The fan runs on high and low if T-stat is on cool but only runs on high if T-stat is set to fan. Same for either auto or manual. I was told if capacitor is bad the compressor should try to start and get warm. It does have 3 capacitors. It does not click or hum at all. The electrical board in the unit says it is a ceiling assembly part number 8330a633

      Thanks for any help you can give me.

    • profile image

      PraireFire 2 months ago

      Hi Randy

      Coleman 48004866 10 years old.Was working fine earlier this summer in 90 plus degree weather for about a month at the lake. Since I brought it home,it has been blowing very little cold and no heat. Replaced all 3 capacitors , cleaned fins with toothbrush. Compressor appears to be cutting in and digital thermostat seems to be working fine? Does not appear to have any freon leaks, just some minor residue on some tubing. Can a heat pump switch be the problem? If so, how do I test and where to locate it?

      Thanks, PraireFire

    • Randy Godwin profile image
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      Randy Godwin 2 months ago from Southern Georgia

      Brian, I've sold some universal fan motors from Amazon in cases like yours. Check them out. Do you have the model number of the AC? If so it should be no problem finding a fan motor replacement.

      Randy

    • profile image

      Brian 2 months ago

      Hey Randy, I have an 89 Prowler and have a seized ac fan motor that I'm trying to replace I cant make out anything on the motor tag as far as a part # goes. Its a 2 speed 110 volt. Is that a standard motor? and where could I find one or a part # would be helpful. Thanks for your help.

    • Randy Godwin profile image
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      Randy Godwin 2 months ago from Southern Georgia

      Hey Tom. check the capacitors first. They can go bad and leak hot oil causing smoke in the process. Of course, at 12 years of age, the compressor or fan could also be suspects.

      You'll have to remove the shroud to see for sure which of the 3--or perhaps I'm wrong as there may be more--is the culprit.

      Randy

    • profile image

      Tom 2 months ago

      Randy

      Have a RV coleman 13500 roof top A/C started blowing smoke out of the vents and had a burning smell --12 years old, Any ideas?

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Mark, check the voltage where the heating element connects first. If you're getting 110-120 volts then the element may be bad.

      Randy

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      Mark 3 months ago

      Hello,my question is about the heating,the air seems to run fine but you turn the heat on runs a minute or two and kicks off same thing every time you try it.but has not ever kicked the breaker .any ideas?

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Raymond, the only way to see if the compressor is bad is to use an amp meter to see if it's pulling more amps than is required. The proper amperage should be on the compressor or on a plate nearby.

      Randy

    • profile image

      Raymond 3 months ago

      Hey Randy,

      So, went ahead and replaced the fan capacitor. But, i was still having the same issue.

      I also double checked to see if the compressor was running and found that it was not. So, I pulled the cover off of the terminals on the compressor and found the Compressor Overload. I tested it and it had .4 ‎Ω. I'm not sure if this was the issue or not, but do you think that means its bad?

      Do you have any suggestions?

      Raymond

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Connie, have the capacitors checked first to see if they've gone bad. If not, the Freon may be getting low as ice forming is not uncommon right before the Freon runs out.

      Randy

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      Connie 3 months ago

      Hey Randy,

      I just bought a used Jayco camper a few months ago to live in and about 3 weeks ago it seemed there was a burning smell coming from the air conditioning unit. We turned it off and then back on about half hour later and it seemed to work fine and we didn't have any issues until about a week ago. I was asleep and I heard something that sounded like beads being slung all over the floor and it woke me up. I couldn't figure out what the noise was so I went back to sleep. The next night I heard the same thing and when I got up to search out what caused the noise I realized that there was little pieces of ice in the floor under where the a/c unit is. I turned it off that day hoping it would defrost itself and then last night it just would even cool at all. The fan works fine and when you switch on the a/c it has that burning smell again and it tries to flip on but then it doesn't, it just keeps trying without success. Any idea what I need to be looking for?

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Chris, have you checked the power at the AC yet? I assume you've already checked the breaker.

      Randy

    • profile image

      Chris 3 months ago

      Hello I need some help I came home today which I'm a full time Rv r my air conditioner has no power so I can't even get power to the control panel any advice

    • profile image

      Raymond 3 months ago

      Hey Randy,

      My AC does have 2 capacitors. The one that i replaced was the Start Capacitor (It was the larger one). Do you think that even though the fan is running fine, that my issues with my AC cooling could be due to the fan capacitor not functioning fully?

      I will double check the compressor.

      Thank you,

      Raymond

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Raymond, your unit may have two caps. one to start/run the fan and the other to start/run the compressor. You should be able to hear the compressor kick on or feel it running. It should get rather warm if it's working.

      Randy

    • profile image

      Raymond 3 months ago

      How do i check and see if the compressor is running?

      I have not. I figured since the fan was running and the diagram said that one was the fan capacitor, that it was fine. Is that not the case?

      Thank you,

      Raymond

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Raymond, is the compressor running at all? Have you tested the other capacitor?

      Randy

    • profile image

      Raymond 3 months ago

      Hey Randy, Thanks for the help. I pulled off the plastic cover and fired up the A/C. The fan turned on just fine so i assumed it was the other capacitor, the run capacitor, as my Coleman - Mach only has 2 Capacitors. I ordered the exact same capacitor and installed it. However, it ac still runs the same as before. The fan will blow high and low, but it doesn't cool. Any ideas?

      Thank you

      Raymond

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      wally kuhns 3 months ago

      Thx for the reply. I pulled the casing and the solder points look fine on the jack where the power cord plugs in. I will trace the wiring further back tomorrow

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Wally, I'd check the connections on the 120 volt AC wiring where it enters the fridge.

      Randy

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Cannot tell you what gas is presently used in your ac, elcaballero. Whatever was originally used can be converted.

      Randy

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      wally kuhns 3 months ago

      Randy - I recently acquired a used Dometic CF50. This portable refrigerator/freezer runs on either 12V or 120V. My unit runs fine on 12V, but no lights or cooling occurs when I plug into 120V. Where do I start troubleshooting? Thank you

    • profile image

      elcaballeroandante52@hotmail.com 3 months ago

      wath is the gas sustitute of rv a/c dometic mod. 1984 in travel trailer Vanguard?

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Justin, have you checked the 12 volt breakers/fuses. The thermostat operates on the 12 volt system as does the fridge and HW heater thermostats.

      Randy

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      Justin Bruce 3 months ago

      Hi Randy,

      This weekend our ac/heat unit suddenly quit working. No power to the thermostat. I checked the breakers and changed the 15 amp fuse for the furnace. Still nothing. No fan, ac, or furnace. Any idea what I can check next? Thanks in advance.

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Brian, you'll have to figure which wires act as a thermostat positive connection. You'll need a thermostat wiring diagram unless you simply rely on trial and error.

      Randy

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      Brian 3 months ago

      I'm working on my duo-therm. I took it off my camper to work on it back at home. How do you wire it up on a test bench without a thermostat?

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Raymond, a new capacitor will probably do the trick. Running an AC from a generator pulls a lot of amps and a weak cap won't do the job.

      Randy

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Carol, follow the thermostat wires as they connect to the control board. Usually an easy replacement with plug ins. You'll probably locate it under a panel where the power is supplied.

      Randy

    • profile image

      Raymond 3 months ago

      Hey Randy,

      I have a pop up camper with a roof ac unit. I took it down to the coast to help with the relief after Harvey. We hooked it up to the generator and it blew on high for a couple minutes then it stopped cooling and only the fan would work. Ive been told that the a capacitor could have blown due to a non grounded generator.

      Any thoughts on that?

      Thank you,

      Raymond

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      Carol 3 months ago

      Hi Randy,

      Where would this control board be found in the AC unit if I removed the shroud? Could I locate it and get a replacement for it and try to install it myself?

      Thanks,

      Carol

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Holly Jo, the smell may have been the capacitor leaking oil when it failed. Remove the shroud on top of the AC and check the capacitor for failure. It should be distorted and the leaking oil should be apparent. If not, either have it checked or replaced. An easy and inexpensive chore in most cases.

      Randy

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      Holly Jo 3 months ago

      ok so yesterday i smelled a weird smell and the lights dimmed as the AC unit turned on like it was trying to power up and couldn't. so I shut it off for the night then in the morning I tried to turn it on again the fan ran then the unit surged like it wanted to but the compressor just hummed...any ideas?

      I have a 1998 Newmar 5th wheel with ducted AC

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      William, have you changed the compressor capacitor yet? An easy to change and relatively inexpensive part to see if the compressor is bad.

      Randy

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      William Lanier 3 months ago

      Colemann mach a/c unit on trailer won't work

      thermostat seems ok,inside blower ok,compressor fan works,but the compressor does not go on,was working two week ago

    • Randy Godwin profile image
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      Randy Godwin 3 months ago from Southern Georgia

      Carol, this could be a bad control board in the AC itself. Even if power is good at the AC end. a bad control board--not to be confused with the control box you installed--will not allow the unit to operate properly. Feel free to ask for more info.

      Randy

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      Randy Godwin 4 months ago from Southern Georgia

      Thanks Jim,and pleased to help. :)

      Randy

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      Randy Godwin 4 months ago from Southern Georgia

      Doug, try changing the capacitor(s) or least have them checked if you don't want to do it yourself. While the unit is turned off use a multimeter set on OMS with the probes touching the terminals. The common should be marked. If the capacitor is good you'll get a random nuber which decreases in value. If bad you'll either get a zero or other steady number. Hope this helps.

      Randy

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      Jim Gaston 4 months ago from Gulf Coast Fl

      Randy thanks for your response to my issue.After closer observation I was able to differentiate a very shuttle change in fan speed. I would have thought the fan would slow down a bit more than it does.

      The good news is the system cools very well.

      Thanks again for your help...Jim

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      Doug 4 months ago

      Randy,

      I have a 99 5th wheel, 30 amp, 1 ac. cooling just fine for about 30 minutes then making noise and quit. I changed out the fan. Now it cooling good for about an hour then flipped the ac 20 amp breaker. Any ideas.

      Thanks

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      Randy Godwin 4 months ago from Southern Georgia

      Jon, this sounds like a bad compressor but you can't tell for sure unless you test it with an amp meter. The proper amps the compressor pulls should be listed on or near the compressor. This could also be a thermostat or control board problem. The process of elimination still works in these cases. :)

      Randy

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      Jon 4 months ago

      My A/C compressor kicks on but only for a few minutes then it shuts off and just blows air. I replaced all 3 capacitors and it is still doing it. It is a 30 amp w/ shedding and it is not shedding at all, the compressor just shuts itself off.

      It is a 97 degree day today and we live in our RV, so it should be on non-stop. It is a Coleman unit.

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Jim, I hesitate to suggest a new control board unless you rule out the thermostat first. It's possible your unit has a separate fan control but it's not likely. Have you looked underneath the shroud yet to see if there's such a relay yet? There may be a wiring diagram on the unit or you can probably find one online using the model number. I'd be interested in what you find out or if any of my suggestions helped. Thanks!

      Randy

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      Jim Gaston 4 months ago from Gulf Coast Fl

      Yes it is a liquid crystal digital and no matter what I move the fan speed the blows on high

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Hey Jim, usually there's a problem with either the thermostat or the control board when the fan doesn't work properly. Is this a wall mounted thermostat?

      Randy

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      Jim Gaston 4 months ago from Gulf Coast Fl

      I have a duo therm roof unit that was replaced July a year ago by the previous owner.

      I notice the blower only works on high speed in spite of it also having a low and medium control on the same thermostat.

      This unit also has a heat strip which also only has a high speed operation.

      Can you give me any help on getting the other speeds to operate?

      Thank You Jim

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      Randy Godwin 4 months ago from Southern Georgia

      Michelle, you may have a bad heating element in the unit. Replacement is not difficult at all. In most cases the element simply plugs in.

      Randy

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      Michelle Kurle 4 months ago

      We have a Air V Carrier for our horse trailer. The unit fits on the ceiling. The air conditioner works but could be colder, but when we turn on the heat it blows but not warm or hot. Any ideas on what to do

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      Randy Godwin 4 months ago from Southern Georgia

      Carol, it may be either the thermostat or the control board. I'd check the thermostat first.

      Randy

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      Randy Godwin 4 months ago from Southern Georgia

      Do you mean the awning, Red?

      Randy

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      Randy Godwin 4 months ago from Southern Georgia

      Keith, it's possible the heating element is burned out. An easy replacement job, if so.

      Randy

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      Carol 4 months ago

      Duo Therm with ceiling manual T-stats control stop working only humming sound on both Fan and Cool when it's "ON" position. Replaced both fan and motor run capacitor. Problem worsen. Doesn't even hum now or try to turn on. Check all the breakers on panel looks good. Check 12V for battery good. Check 120V coming in good. Any clues or ideal Randy?

      Thanks for having this thread running for so long. Very helpful!

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      red 4 months ago

      how do I troubleshoot my owning

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      Keith 4 months ago

      My duo therm unit does not blow hot air. Any ideas

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      Randy Godwin 4 months ago from Southern Georgia

      Hey Steve, have you checked the thermostat yet? It's not uncommon for a thermostat to fail. If it's not the thermostat then the control board may be the culprit. Since you've already changed the fan capacitor and the fan runs when turned to ON, I see no other options.

      Randy

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      GrandpaSteve 4 months ago

      Coleman Mach cooled but fan did not run in auto or on positions unless the squirrel cage was bumped by hand. Motor spins free but would not restart when in auto and T-stat calls for cool. It would run in fan on position.

      Changed fan capacitor and automatic mode worked properly for a few days and now fan won't come on in automatic. Switch to on and fan runs and unit cools.

      Where do I need to look next?

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Tony, it could be the thermostat or the control board. Check the thermostat first.

      Randy

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      Tony 4 months ago

      I have a Salem the air conditioner won't shut off automatically no matter what temp I put it on. Just stays on. Can anybody tell me what

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Your wife may be right, James. A new capacitor is cheap and worth a try before replacing the fan.

      Randy

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Chris, check the compressor capacitor as this may be the problem.

      Randy

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      Randy Godwin 4 months ago from Southern Georgia

      Ian, check or replace the capacitors first.

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      James dewitt 4 months ago

      I have a 2004 Alpenlite 5 th wheel with a heat pump, I have to nudge the fan. And after that it runs like a charm. I think I need a new mother my wife wants to change capacitors. Any thoughts

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      Chris davis 4 months ago

      Hi Randy I have a 2007 kz. The ac will turn on and blow on fan and on ac. Hight or low. I do not hear the compressor kicking on at all. Only hot air will come out. If I turn the ac on and it's blowing air even if I mess with the thermostat put it up to 90 still blows don't shut off and won't blow cold.

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      Ian 4 months ago

      2010 Winnebago Itasca. Rear rooftop Coleman air starts and runs blowing cold air for about 3 mins. The blower fan then stops but unit still runs for a couple more mins before shutting down.. Thermostat seems to work fine. Come back in 15 mins and try it again and it does the same thing.

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      Randy Godwin 4 months ago from Southern Georgia

      It does indeed seem the thermostat is faulty, Mike.

      Randy

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      Mike 4 months ago

      Still have issues, however I did find that I can touch the two thermostat wires to the furnace together and it kicks on, and if I put a jumper from R to Y my AC unit comes on. The red wire get hot if it's on heat, but having the theomostst hooked up normally, all that will come on it the fan on the AC unit. Any suggestions as to what may be causing this? I figured the thermostat may be defective, because I will told by mautiple RV service people that the thermostat I have will work in a camper, I went as far as replacing my wires from my AC to the thermostat and still only get the fan. Placing jumper wires everything works as it should but won't shut off unless it's disconnected. I had a Honeywell RTH2300b installed with my new AC unit and the control box is all brand now.

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      John, it could be a bad capacitor. An inexpensive and easy replacement in most cases.

      Randy

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      John 4 months ago

      I was camping and the ac stopped cooling I switch to the back ac tell I could get up on the roof I seen that it was wet around the ac so I tried to start the ac and the fan would turn on but no cold air what could be wrong with it

    • Randy Godwin profile image
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      Randy Godwin 4 months ago from Southern Georgia

      Brian, a weak capacitor will cause this problem, especially when powered by a generator.

      Randy

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      Brian 4 months ago

      hello randy,

      my main cabin ac will not turn on. With the generator on, I turn it to high and cool. You can here the generator surge a little like it is drawing from it. Under the ac unit it makes a loud humming noise and acts like it wants to turn on but does not. the rear ac works fine

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      Randy Godwin 4 months ago from Southern Georgia

      Wade, more than likely it's the thermostat or the control board causing the problem. Have you checked the thermostat voltage yet?

      Randy

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      wade 4 months ago

      compressor running with thermostat turned off

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      Randy Godwin 4 months ago from Southern Georgia

      Brad, I assume you've checked the thermostat if you have a wall mounted model, so that only leaves the control board or a bad compressor. It seems odd though that the compressor was working fine when you turned it off before the two week absence. Does the AC do anything at all, make noise, try to start, etc?

      Randy

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      Brad Langley 4 months ago

      coleman ac unit turn off left for 2 weeks came back compressor would not start up replaced all 3 capacitors compress still won't start it is an 08 year model might be time for a new on don't what else to check any suggestions

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      Randy Godwin 4 months ago from Southern Georgia

      Rodney, try replacing the fan capacitor and see if this solves the problem.

      Randy

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      Rodney 4 months ago

      Hi Randy. I have a 2006 Dutchmen 31ft with a Dometic Duo Therm that started making a funny noise, but every time I restarted the ac act like normal. Yesterday the ac was making that noise again, the air it is not blowing so strong as should be. It looks like still blowing cold. I try the fan only, and looks like the fan is not blowing strong. Any chance could be something easy to fix?

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      Randy Godwin 4 months ago from Southern Georgia

      Jay, sorry the new fan motor didn't fix the problem. Are you sure the breaker is good?

      Randy

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      Jay 4 months ago

      Hello Randy. I've been very busy and actually just got around to installing a new fan motor. Unfortunately, I do not have good results.

      The install was a bit of a pain because the A/C unit is very old. There was no way for me to access the squirrel cage to loosen the motor on that end because it was shielded all around and sealed; so I cut into the encasement and was able to access the screw on the squirrel cage at that point. (When I finished replacing the motor, I used aluminum tape to seal the opening that I cut and bent open).

      Well, the end result was that the breaker still trips. I've replaced 2 capacitors and the fan motor & fan blade. I think I'll call it a day and decide if I'm willing to spend another $500-$600 on a new unit, then spend half the day removing the old and installing the new.

      Thank you for your input. It was most appreciated.

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      Randy Godwin 4 months ago from Southern Georgia

      Doug, try using some good no-rinse spray coil cleaner as dirty coils can cause the unit to disperse the moisture onto the roof or down through the filter.

      Randy

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      Doug 4 months ago

      I have a 2007 Jayco Eagle with a Coleman AC unit. Water from the condenser runs out on to the roof of the camper. Is this normal.

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      Randy Godwin 4 months ago from Southern Georgia

      Dustin, was it blowing cold air before the cleaning?

      Randy

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      Dustin Acker 4 months ago

      Anyone have any ideas why it won't blow cold air after cleaning?