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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    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      18 hours ago from Southern Georgia

      Tina, I'm not familiar with a fuse or breaker being in the AC unit. This would be not be necessary with the breakers in the 110 volt power panel handling this issue.

      There is an automatic reset on many ac's, but you don't have to manually reset them. Are you sure you don't have a bad capacitor? This will cause the AC not to start.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      18 hours ago from Southern Georgia

      Dan, this doesn't seem to fit your description of how cool the air really is. I'd question this if I were you.

      Randy

    • profile image

      Tina 

      19 hours ago

      a/c not running - no noise, has power; did this last winter and took in for repair, was told there is a fuse up in the a/c unit itself? Fuses and breakers under bed look ok. Do I have to access that from roof? where to look?

    • profile image

      Dan 

      21 hours ago

      test of truth have a new RV with coleman units the front AC unit does not seem to be blowing cold air just sort of cool. was told by the shop foreman that these are designed to only put out air that is 20 degrees colder then the air around them or room temp true or false

      jdnagle1@msn.com

      thank you

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 days ago from Southern Georgia

      Acemonsoon, sounds like a bad capacitor. About $25 to replace and normally a simple chore.

      Randy

    • profile image

      Acemonsoon 

      2 days ago

      So my ac in my 2008 c class doesn’t blow very cool air at all. The fan functions low high etc not a big difference in temperature when u switch it to cool? Any thoughts?

    • profile image

      Mike Sellards 

      3 days ago

      you suggested i check the capacitor start capacitor or run capacitor

      Mike, you may want to have the capacitor checked first. If they're okay, then the thermostat and control board are suspect.

      Randy

      profile image

      Mike Sellards

      20 hours ago

      I have a 2013 A/C unit that blows cold air on startup but after 15 min or so it will only blow warm air. Any idea what could be causing that

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      Ron, this may be due to a bad thermostat or the control board. Check to see if the thermostat is getting a 12 volt power supply first.

      Randy

    • profile image

      Ron 

      4 days ago

      Have a airxcel. Roof mount. Heat pump. 2 year old Jayco motor home. No heat, no cold air. Fan works. No circuit breaker bad. All fuses good. ? ?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      David, this may be due to a weak capacitor. Have then checked first.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      Andrew, first have the capacitors checked and also clean the coils if you haven't already done so.

      Randy

    • profile image

      David 

      4 days ago

      Hi Randy.........During the hottest part of the day my AC unit will stop blowing for about 5 seconds, but continues to make a humming sound, then comes back on. It will do this several times. When evening comes it runs normal. It cools well other than that. I have a voltage monitor and when it stops, the voltage goes from 115 to 110. Thanks.

    • profile image

      Andrew 

      4 days ago

      Good day, my AC unit will blow some cold air but not enough to cool the camper down and will also sputter some times.....any thoughts?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      Mike, you may want to have the capacitor checked first. If they're okay, then the thermostat and control board are suspect.

      Randy

    • profile image

      Mike Sellards 

      4 days ago

      I have a 2013 A/C unit that blows cold air on startup but after 15 min or so it will only blow warm air. Any idea what could be causing that

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      Whoever you are with the AC which won't cut off, this is either a thermostat or control board issue. Check the thermostat first.

      Randy

    • profile image

      The AC in our 35ft trailer will not shut off 

      4 days ago

      We cannot get our AC to turn off after it has rwached desired temp

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 days ago from Southern Georgia

      Sybil, this is usually due to very dirty coils. Are you sure you've cleaned the coils well with a cleaner especially made for such? Sometimes it's tough to get to the coils to clean them without removing some of the covering. Otherwise, are you sure the gasket is tight between the AC and the roof?

      Randy

    • profile image

      Sybil 

      5 days ago

      Our ac works great but drips water inside the camper. We have clean everything on top of the camper. Any suggestions?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      5 days ago from Southern Georgia

      Betty, I sell a few AC's from Amazon and they seem to work well. Any rooftop AC unit will fit the hole where the old unit is now. All campers use the same size openings for the AC unit.

      Randy

    • profile image

      Betty Baldwin 

      5 days ago

      I was told I need Freon in my ac. But it can not be replaced, so we will need a whole new unit. Can you help me. We have a 2012 Komfort

    • profile image

      Jim 

      5 days ago

      Missing contactors

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      6 days ago from Southern Georgia

      Tom, you have two coils. One a condenser and the other an evaporator coil. If you have a roof mount AC, both are on the roof.

      Randy

    • profile image

      John 

      6 days ago

      Carrier unit was running fine blowing cold air turn it off for about an hour to come back turn it on now it's blowing hot air what to do

    • profile image

      Tom 

      6 days ago

      Its not on the roof. The condenser is where the high side gets cooled outside. Can't find it & its not on the roof.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      7 days ago from Southern Georgia

      Charles, try some no-rinse spray coil cleaner from ACE Hardware or from Amazon. Be sure and clean both coils well.

      Randy

    • profile image

      Charles Diettrich jr 

      7 days ago

      How to clean dust clogging up unit?,up inside unit

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      7 days ago from Southern Georgia

      Mark, yes the thermostat is suspected.

      Randy

    • profile image

      Mark Labus 

      7 days ago

      If my RV’s AC does not run on the “auto” setting, could that mean my thermostat needs replaced? Seems to run fine otherwise.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      9 days ago from Southern Georgia

      Carl, thanks for returning and relating how reversing the shaft worked for you. This info may help others with a similar problem. :)

      Randy

    • profile image

      Carl 

      9 days ago

      About 2 weeks ago I asked you if I could change the long shaft to the short side of my ac ,motor. I needed to keep the rotation the same but switch the shaft. I took the end cap off of one end of the motor. I turned the armature around and stuck it back in. I works fine. the rotation is still correct and now the long and short shaft are correct also. Thought you may like to know. Thanks. Carl

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      9 days ago from Southern Georgia

      Nicole, this is usually a bad fan motor capacitor. Around $25 or so and easy to replace in most cases.

      Randy

    • profile image

      Nicole C3Hann 

      9 days ago

      I have a Dometic, Comfort Control system the heat strip stopped working last Oct. The ac had been working fine which I checked several days ago. I turned on yesterday & everything seems fine but the fan won't kick on. I've checked the fuse, which was fine. I do hear a click at the over head power box but i've heard before & the fan usually comes on right after but nothing now. I checked the top unit & the fan moves freely. Can you give me an idea what this might be? Thank you!

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      9 days ago from Southern Georgia

      Logan, more than likely the compressor capacitor is weak. About $25 and easy to replace.

      Randy

    • profile image

      Logan Dooley 

      10 days ago

      I have a jayco pop up with a Coleman a/c. The fan runs like it should on all settings. The compressor will sometimes start and work great or other times will not kick on and make a humming noise for about 5-6 secs and stop. It continues until it finally starts. Any ideas ?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      10 days ago from Southern Georgia

      Clint, have they been removed lately for maintenance or replacement?

      Randy

    • profile image

      Clint f 

      10 days ago

      I have 2000 alfa with dual compressors but the they seem to be running backwards blowing hot are in camper any suggestions??

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      12 days ago from Southern Georgia

      Kelli, are you sure the compressor is running?

      Randy

    • profile image

      Kelli Barbella 

      13 days ago

      We have a 2017 Winnebago Sunstar. The front AC (Coleman Mach) is not cooling. Seems to be cycling correctly, air is blowing from the vent and filters are clean. Thoughts on troubleshooting. Thanks!!

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      13 days ago from Southern Georgia

      Jim, I don't have the info you need, but you should be able to get the info from the maker of the unit. All you need is the model number in most cases. Good luck!

      Randy

    • profile image

      Jim steeg 

      13 days ago

      I have a 2007 Fleetwood expedition motor home with a roof top air conditioner/heat pump and the 3 speed, 5 wire fan motor (double shaft) has gone bad. There is no model number or serial number available because the printing has faded to bad. The pamphlet that came with the motor home just says RV products. Can you help me? It would be greatly appreciated,

    • profile image

      George Guilford 

      13 days ago from Clarksville TN

      Capacitor replaced, AC working great!! Good luck to anyone else who has this issue

    • profile image

      George Guilford 

      2 weeks ago from Clarksville TN

      Randy, I will update tomorrow after I get it. After letting it sit for a while and while I was on top of camper, I turned unit on again and could hear the compressor humming like it was trying to turn on and after about 2-3 seconds it would stop. I am hoping it is the capacitor cause it really sounds like it is not getting that extra boost it needs to start.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      George, it sounds like the capacitor is the problem. Let me know if it isn't.

      Randy

    • profile image

      George Guilford 

      2 weeks ago from Clarksville TN

      Coleman Mach AC unit is blowing hot air. The fan is running and when sitting inside, the tone of the fan decreases and I hear a low humming for 2 sec and when the 2nd humming stops, the fan tone goes back to previous. Like compressor is drawing current trying to start and fan slows. I have found the capacitor for it (cannot check) and was going to replace tomorrow. I went a little further and found the overload on top of the compressor which with wires connected has a reading of 1.2 ohms. Is that good or bad? I would think good. ANy help is appreciated

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      RDennis, either the unit is low on Freon or the thermostat is haywire.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Carolyn, disconnect the power at the thermostat as it runs on the 12 volt system.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      S Thatcher, you can carry them to a local AC service and they'' check them and give you the correct replacements if necessary.

      Randy

    • profile image

      RDennis75 

      2 weeks ago

      I have a 2014 Coleman Ducted AC unit, the coils keep freezing over and it just does not cool the camper as it should. I have changed out both capacitors and also cleaned the coils. what could be wrong?

    • profile image

      Carolyn Sharp 

      2 weeks ago

      We shut off the breaker to the A/C unit as it’s old and we do not need it/use it. The thermostat is turned off but the unit just constantly makes a ticking sound. How do we make it stop?

    • profile image

      S Thatcher 

      2 weeks ago

      randy,

      disregard the last post. i have a coleman rv unit, it has 3 capacitors, 2 run and 1 start. the start has a resistor on it but the replacement does not. do i need the resistor on it? when the unit stopped working it sounded like the fan was just winding down then stopped. which capacitor should i change first?

    • profile image

      S Thatcher 

      2 weeks ago

      on a coleman ac unit how do i tell which capacitors (3) to purchase when the capacitors do not have all the information that i need on them. ie: no vac # or mfd #. They show mrp #'s on one of the 3 but nothing on the others. can i find out the info needed from misc info on the capacitor itself? does aeromet mean anything? it also has #'s that follow a M. M22P370700 is one of them

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Brian, if you're sure the compressor is running and the caps are good, then this may be a restriction in the system. If you can rent or borrow a clamp-on amp meter, then you can see if the compressor is drawing more amps than normally required according to the info on the compressor or on a plate nearby. But usually if this is the case, the breaker will trip.

      Randy

    • profile image

      Brian Fike 

      2 weeks ago

      Randy,

      I have a standard 15k Dometic, sudden loss of cooling last week. Fan blows, compressor appears to come on, coils have been cleaned. Never experienced coil freezing up, so i don't think it was a low refrigerant that wound up leaking out. Father-in-law says probably the compressor, even though it looks like it's coming on. Any ideas? Thanks so much for your site here, extremely informative and you have obviously helped a lot of people.

      -Brian

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Joe, I can't help you with a store near you, but you should be able to find the part online.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Janet, do I assume you're trying to power the AC with a generator?

    • profile image

      Joes in FLA 

      2 weeks ago

      Randy

      Where in Fla can I buy thermal overload switch for Mach 1 AC 1/4 hp ? The number stamped on the old one is MRA2771-499. The closer to Clearwater FLA, the better for me, but I’ll drive wherever I need to.

      Thanks for your help

      Joe

    • profile image

      Janet younker 

      2 weeks ago

      What do you think my issue could be? I turn my ac on in the rv and it trips the automatic transfer switch shutting my ac and recepticals down. When I turn the ac off the recepticals regain power. I thought it was my ac so I purchased a new ac unit still does the same thing. If I plug into electric the ac works fine any help would be appreciated. Thanks Janet

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Jimmy, check or replace the capacitor(s) first as this is a rather cheap and easy chore. Hope this solves the problem, but if not, let me know. Good luck!

      Randy

    • profile image

      Jimmy Bryant 

      2 weeks ago

      Hi Randy: We bought a 2010 Sunset Creek with a Dometic AC. Worked great first day. Second day AC worked for 30 minutes and tripped AC breaker. Kept trying to turn on breaker but it immediately trips. Turned everything off to reset thermostat . After 30 minutes tried it, and breaker stays on , but AC dosen't do anything, except click when adjusting temp on thermostat. What could this be ? Thanks buddy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      Rezzonico, I can see no reason why the AC's would work off of the generator while stopped, and don't work properly when the vehicle is in transit. Could be something to do with the 12 volt thermostat not getting a signal when unplugged from the shore connection, but this is simply a guess.

      Randy

    • profile image

      Rezzonico 

      2 weeks ago

      Hello Randy,

      Thank you for this site. We have a 2015 Southwind 32 with two dometic roof airs. When we drive, in hot weather, we run them off the Onan 5500 generator. After 20-45 min they stop functioning, even tho the generator is still running. We stop the generator, reset the main cabin and aux. rocker switches, wait a bit, then power up, and after a bit they come back on only to do the same thing again, in a matter of time. We have tried running just one, but the same result. At night, when sleeping, they work off the generator, as designed, no problem. Any thoughts?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      2 weeks ago from Southern Georgia

      CoveredWagon, have had the capacitor for the AC compressor checked and/or replaced yet? If not, then try this next. It's not unusal for a weak cap to do this when powered by a generator

    • profile image

      CoveredWagon 

      2 weeks ago

      Randy,

      I just replaced my a/c with a refurbished Mach 15. Although it will run on shore power, it will not run on my generators. Even with all appliance turned off or disconnected the start amps trip the 30 amp breakers on the generators. I have tried the onboard Onan and a stand alone 4000w generator. This was purchased from http://www.rvproductsshop.com/. It was shipped from the MFG. There is only 2 run capacitors installed but no start cap with PTCR. Any clue what the problem could be?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Joes, I sell many AC units from Amazon and so far I haven't any complaints. I may have a link on this page. Any AC will fit in the existing opening where the old one was as they use a standard opening the same as a regular vent opening.

      Good luck and feel free to ask for more info if needed.

      Randy

    • profile image

      Joes in FLA 

      3 weeks ago

      Hi Randy, I’m looking for a replacement of thermal overload switch on my Rooftop AC unit Coleman Mach 1 1/4 hp compressor. I have tested it and it’s shot. I have temporarily bypasses the switches and now it’s running ice cold again. But I don’t want to push my luck. Do you know where I can find a replacement? It’s a 1982 Coleman unit with a 1/4 hp compressor. The switch has this number on it: MRA2771-499. Thank you, Joe

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      JC, try turning off the 12 volt main breaker and see if the noise stops. If so, it may be the thermostat still sending a signal to the control board as it works on the 12 volt system.

      Randy

    • profile image

      JC 

      3 weeks ago

      Just replaced rooftop unit with a new one because of busted coil. The new unit makes a buzzing noise as if the fan motor would be trying to come on as soon as the breaker is turned off even with the thermostat in the off position. Might this be the controller causing the problem?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Ronnie Sue, yes it's relatively easy to replace a capacitor. You probably have one each for the compressor and fan motor. Just be careful when changing the caps to not touch the terminals with your bare hands unless you discharge them first by crossing the terminals with a screwdriver.

      I sell a lot of capacitors from Amazon which is where you can go to see what you're looking for and for finding a replacement capacitor.

      Cost around $25 or so.Just remove the shroud to access the caps. Good luck!

      Randy

    • profile image

      RonnieSue 

      3 weeks ago

      i have 3 Dometic 15000 BTU A/C units, model is either 630515 or 630516. we are on 30 amp service and have been running only 1 unit at a time. It's very hot here (100+) and we left one unit running while we went out for the day.

      we came back to find the circuit breaker was tripped and of course the a/c unit was off.

      we are getting the motor to run, but no cool air. i read a comment/article here which makes it sound like a capacitor? do you have any suggestions as to what my next step is? if it is a capacitor, is that something that is easy (for a handy person) to fix? where to purchase capacitor? thanks so much. i'm glad i found this website!

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Zachary, I assume you mean the compressor instead of the condenser? I still suspect the control board.

      Randy

    • profile image

      Zachary 

      3 weeks ago

      Sorry for the multiple comments.

      I just went back inside and did Reset on the thermostat (removed fuse for 5 minutes and re-programmed for the type of system)

      Nothing would turn on.

      Repeated the breaker/remove/replace fuses as earlier.

      Both ACs came one, but zone 1 still warm air.

      After 15 minutes zone 1 is now cold.

      So whatever it is, it's causing the condenser to work intermittently.

      ps, I did notice the LED on the circuit board was solid green.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Lucero, probably a bad fan motor capacitor. About $25 or so to replace.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Tom, have the compressor capacitor checked and/or replaced.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Thanks so much, Richard. I'm pleased to have been of help to you. You're very welcome! :)

      Randy

    • profile image

      LUCero 

      3 weeks ago

      ONLy make noise doesn’t turn fan

    • profile image

      Tom 

      3 weeks ago

      Air conditioning fan runs but compressor doesn't start?

    • profile image

      Richard 

      3 weeks ago

      Hey Randi, I want to thank you for what you do, It turned out to be a bad thermostat, I jumped the wires and the blower came on. It’s people like yourself that make life a little bit easier for us DYIers. You are a true American, God bless and once again Thank You.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Louise, what happens when you turn on the AC? Does it trip a breaker, or stall the generator out?

      Randy

    • profile image

      louise allen 

      3 weeks ago

      onan 4000 emeral generator starts runs tell I turn roof A/C on in rv new to rv help

    • profile image

      GLENN DESOTO 

      3 weeks ago

      thank you I will try that and let you know

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Donna, this may be either thermostat of the control board causing this issue. Check the thermostat first.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Glen, more than likely it's the thermostat or control board causing the problem. I'd try replacing the thermostat before the control board.

      Randy

    • profile image

      Donna 

      3 weeks ago

      My account comes on and blows cool but keeps turning off and on. What could this be

    • profile image

      GLENN DESOTO 

      3 weeks ago

      I have a 2012 tour with 3 units and 2 zones zone 1 zone has 2 units on it and I am having trouble with one of them the unit comes on fan blows compressor is not getting voltage all 3 of the capacitors or good the pressure switch is good I dont know how to jump the units compressor to see if it will come on but my best guess is 1 thermostat or 2 control box failure .I dont know how to test the thermostat I am told the control board has a set of wires marked SHED that I could try removing one of the to see if the power management system is (shedding power ) can you comment on this issue or give me any other tips please

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Boone, if the coils are clean then this may be a weak capacitor. Around $25 and easy to replace.

      Randy

    • profile image

      Boone 

      3 weeks ago

      Randy, my account works good at night but in the day the fan works but the compressor keeps dieing. I am at a campsite and the power might be struggling in the day. I just tested it at night to see if it works. In the day it runs for only 5 minutes tops. Last night 45 tell I shut it off.

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      3 weeks ago from Southern Georgia

      Nick, first check or replace the compressor capacitor if it's bad. About $25 and easy to replace.

      Randy

    • profile image

      Nick 

      3 weeks ago

      Hey, so man fan comes on but I can’t hear the compressor come on...

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      James, yes it has to have 110 volts to run the AC.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      Mason, you didn't say, but I'll bet you have a ducted system in your camper. The ducts in some campers are notorious for collapsing and causing this problem.

      You may be able to spread the ducts back out by running a stick with a small block--smaller than the duct size--through the vents. You may have to do this from vent to vent to be sure the ducts are open again. Hope this works for you!

      Randy

    • profile image

      Mason 

      4 weeks ago

      A/c is on but not blowing through out the rooms and not blowing hard whatsoever what is the problem?

    • profile image

      James Wilson 

      4 weeks ago

      does the roof mounted AC only run when plugged in?

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      Richard, go online and find the correct control board for your AC and you'll find what to look for. It should be easily seen when you remove the AC shroud. It's a circuit board which unplugs from the thermostat wire and other wires going to the compressor and fan motor.

      You may be able to find the board on Amazon as I've sold many from there.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      Carl, can't help you there as I'm not an electric motor expert. You may ask as the local electric motor repair shop if this is possible.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      Amanda, I'm sure you can find the info online if you really want to buy or rent the tools you need. And no, auto Freon would not work.

      Randy

    • Randy Godwin profile imageAUTHOR

      Randy Godwin 

      4 weeks ago from Southern Georgia

      Ricardo, this is probably a thermostat or control board issue. Check the thermostat first before replacing the control board.

      Randy

    • profile image

      Richard Liciaga 

      4 weeks ago

      I will have to find the control board, that termostat was changed out last year when it died on me. Is that control board located on the AC unit?

    • profile image

      Carl 

      4 weeks ago

      I have a 96 40 ft Allegro bus. The fan motor on one of my ac units is bad. I bought a new one from Dyer Rv parts. I noticed that the long and short shaft was backwards from the old motor. But the rotation was the same.Can I take the end cap off of the new motor and turn the armature around to make the long shaft on the other side ? Will it still run ? Thanks . Carl

    • profile image

      Amanda 

      4 weeks ago

      My central AC n the RV blows cold air but can't keep up in the heat of the day we have vacuumed the coils & sprayed them with water to remove the build up which did help a Lil... U said only a trained professional should/could add freon...so I'm assuming we can't use the recharge for a vehicle? My ol man & I r both DIY Mr fix its... Is there a website, book, or n e thing where I can get instructions on adding freon

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