Air Conditioner Questions

by Bursby (Ohio)

Question: My RV air conditioner just stopped working. It will not do anything. Where do I start to figure out the problem? It was working just fine, then shut off. Also, what is the best RV air conditioner out there?

Answer: As you might expect, diagnosing this kind of a problem remotely is difficult at best. Fixing an AC unit can involve knowledge of electrical, mechanical, and electronic systems.

There are also many differences between the various air conditioner brands and how AC systems are configured in the multitude of RV types and models. So we can only offer some thoughts on how to approach the problem. And since we are familiar with Dometic Air Conditioners, these suggestions are based on that frame of reference.

In order to troubleshoot the problem, you should have a good mechanical and electrical aptitude, your AC owners’ manual, thermostat owners’ manual and a working knowledge of electronics.

Minimum tools needed: Volt/ohm meter (there are many different types available), screwdrivers, diagonal pliers, electrical tape, flash light.

Safety: Remember you will be working on live circuits, moving parts and are going to be on the roof of your RV. Remember to keep your fingers away from moving parts and make sure you do not cause more damage than what you had when you started. It may be more cost effective to let a professional fix your problem.

If you don’t feel comfortable or sufficiently knowledgeable about any of the following, then you should take your RV to a competent RV repair shop that specializes in AC repairs. We are not experts in this area – we are simply offering a few basic areas to check:

Start with the obvious, inside the RV:

  • Is your thermostat on and is it set to a lower temperature than the inside temperature of your RV?
  • Are the AC circuit breakers tripped? If so, reset them by fully turning them off and then putting them back on. Remove the breaker and using your volt meter, check the power supply to the breaker. If you have power, reinsert the breaker and reset it.
  • Remove the AC cover where the filter normally sits. Turn on the air conditioner, do you smell or see anything out of the ordinary like obstructions or burned wires?
  • Check for loose or broken wires. Here you will also see one or more RJ11 connectors and cables (like phone cables). Disconnect them and reconnect them and make sure they are well seated. Make sure you do this one at a time if more than one cable is found, and do not reconnect them improperly.
  • If needed, clean the male end of the RJ11 connection with an eraser, carefully plug and unplug the connections a few times.
  • Go to your thermostat and carefully remove the thermostat from the wall and see if you can disconnect and reconnect the cable.
  • Do a reset of the thermostat if possible (see your owner’s manual for proper steps).

Next – Check things outside:

If you still have a problem then you will need to get up on the roof to do further checks and tests. If you are not comfortable working on the roof or working with electricity, don’t do it.


  • Move to the roof and remove the A/C shroud and access panels to the motor and electrical elements.
  • Using your volt meter check for power to the motor If you have power, then make sure that the amperage/voltage readings are good (see your owner’s manual).
  • If you do not see the proper amperage or voltage then you need to check for continuity. If there is a loss of continuity then check the wires for loose, broken, or corroded connections. You may have to open up connections and redo them. You may have to trace the circuits all the way back to the breakers.

The Control Board:

  • Visually inspect the control board. On our unit, the board is located under the A/C shroud, on the curbside under an access panel.
  • Do any of the connections into or out of the control board look loose, broken, or burnt?
  • Do any of the components look discolored or scorched? Is there a smell of burnt insulation? If you find a loose or broken wire, fix it. If you find something out of the ordinary with the control board then you may be able to replace it or go to an RV repair facility for the repair.
  • Check the thermistor for proper operation, Connect your volt-ohm meter to the thermistor lead and apply heat to the cooper wire. If there is a drop in resistance, then the thermister is good.
  • If the AC problem is still not resolved and if you feel comfortable and knowledgeable, you could go further to check the capacitor(s) and relays for proper operation. Personally, we would not do this ourselves and would instead use a qualified service facility with expertise in AC units and systems. If you plan to replace your air conditioner instead, here is a good list of the best RV air conditioner. You may also want try out a portable air conditioner, which tends to be less complicated and easier to maintain.
May 29, 2016 Ac problem
by: Zach

My freeze control sensor switch is disconnected and my a/c doesnt get cold where does that have to be connected and where if so please help

Jan 01, 2016 No power to AC unit
by: Jack

Have checked power lead to unit – dead. Tried to trace where lead goes with difficulty. Any suggestions?

Jul 23, 2015 Cheap Fix in a bind
by: Danny Roland

I had an A/C do something like this and I traced it down to the board that controls everything. I could not get a board in time for me to leave on a trip so I bought a Transformer 120 to 24 volt two relays, and a regular house thermostat and hooked them up and my A/C works fine all for about $50.00 (pulled out control board and threw it away)

May 12, 2015 A/C quirk!
by: Daniel

When using our A/C in our 2014 Coachmen FR Exprs camper for first time, it did a crazy thing….After connecting to Elec. we turned it on and it was running for a few minutes and then fan cut off, but compressor was still running and then the fan came back on in just a few seconds. It did this crazy thing several more times and finally ran normally for the 3 days we camped. When we got it home and plugged in while we were cleaning, it happened again. What could this be. We bought it from individual in Oct., they had bought it brand new and only used 3 times. This was our first real camping experience in it. We are longtime campers…..have owned almost every type over 40 yrs of marriage.

Mar 09, 2015 A/C Fan will not go off. Does it stay on all the time?
by: Joe

My Dometic RV 15K A/C cycles off with the compressor but the fan stays on. Is the fan supposed to stay on all the time?

Feb 08, 2015 Air Conditioner Tripping Breaker
by: Anonymous

The air runs for 30 seconds or more and then the breaker kicks off. Help!

Oct 23, 2014 No light at the thermostat?
by: Jose

Regarding your 1997 Holiday Rambler AC problem…

If your thermostat is not indicating a zone or has no readings, then you have lost the communications link between the thermostat and the a/c control board. If you have your a/c operators manual you might be able to follow the instructions for resetting it. This may reestablish the communications link. Or you could remove the thermostat and gently remove the phone like connector at the back of the thermostat and plug it back in. If that does not bring you back then we suggest you contact the a/c manufacturer for help in diagnosing the problem or seek professional help.

Oct 23, 2014 Holiday Rambler Vacationer
by: Anonymous

I have a 1995 27ft model and have no idea as to why my ac does not work. It used to operate with no problems. Now there are no lights on wall mounted thermostat. I have checked the CB and reset. Still nothing. There must be another fuse somewhere but looking in the manual I cannot find it. Any ideas??? Thanks.

Air Conditioners Will Not Turn On

by Ben L. (Mountainair, NM)

Question: My Acs won’t turn on, even when plugged into the 30 amp outlet. I was going to replace my two 6 volt batteries on my RV. I pulled them out and took them to my local auto parts store and with no luck, went back to the RV. I reinstalled the two batteries back to the way they were hooked up and now my air conditioners are not working.

The lights come on on the thermostats controls but it acts like there isn’t any power flowing to them. Does anybody know what may have happened or how to fix this? The RV is hooked up to a 30 amp connection, but still nothing.

Answer: We suggest you do the following:

Reset the outside power breaker
Then reset the air conditioning breaker(s) 120 volt side
Does the a/c work?

If no, continue on only if you are comfortable working on the roof of your RV and you have a basic knowledge of 12 and 120 volt electrical circuits. If you do, then feel free to continue at your own risk. However, you will need some basic tools like a nut driver or sockets, screw driver and volt meter and or test light. Remember, if you make a mistake it may cost you far more than having a professional take care of the problem.

Here is a link to a Dometic service manual. If you do not have a Dometic air conditioner, you can probably still use the same troubleshooting guidelines since they all work about the same.

Go to section C15 – look at the diagram below the description for the location of the fuse on the ccc power module. Check the fuse and replace it if needed. The description in C15 seems to fit perfectly with your circumstances.

If this does not solve the problem then you will have a choice to make. Call a professional or go on with your diagnosis. If you feel comfortable continuing, then go to the service manual section E – Trouble shooting – Go to symptom 1 – The unit does not run…. etc.

Then chose the correct type of control system that matches your situation. Our guess is that you have a Comfort Control Center. The others are for older type units. Follow the outline under “Cause”, go to Configuration in the next column and it will tell you the section of the manual dealing with that cause (no need to do Fuse, you did that above). Then go to next step and so on.

Hope this helps. Other input welcome.

Dec 12, 2015 I need help
by: Anonymous

The a.c.on my rv is making weird loud sounds it turns off and on the the lights go low and it’s clicking loud

Sep 24, 2015 new rv 3 acs in one year
by: Anonymous

I have replaced 3 Dometic air conditioners in one year

Jun 23, 2015 Thank you so very kindly
by: Anonymous

Thank you for allowing me to check the obvious when at times the obvious appears hidden. Got the AC fixed thanks to you and your wonderful site.

Air Conditioner Voltage Toy Hauler

Question: The air conditioner seems way too inefficient – it does not cool much at all. We have had it checked twice and we are told this is working as it should. Just wondering of anyone else has experienced the same thing.

Answer: We are posting your question in case other Voltage owners have input. You may also want to search online for forums or a Voltage owner’s group which addresses topics specific to the Voltage Toy Hauler.

Jul 30, 2012 Check it with a thermometer
by: Jay

Compare the temp of the supply and the return air. If there is at least a 16 degree temp split between the two, your unit is working as designed. If not, you, there is a problem with it.

Jul 16, 2012 A/C
by: VoltageOwner

I know they are now offering a third a/c option. Maybe this will help?

AC Clearance

by Joe (New Orleans, LA)

Question: When my RV is parked under covered storage and I am running both AC units, how much clearance should I have between the top of the AC and the top of the ceiling to get proper ventilation?

Answer: Good question. We looked through our manuals and the internet but could not find a reference for a overhead clearance for an A/C unit on an RV. Having said that, we suggest that you keep the grill openings clear of any obstructions. We can only speculate that all you need is a few (3-6) inches of clearance overhead, but that is just speculation on our part.

Also, have you tried to lower the RV to its lowest height? On our RV we can lower our unit about 8 inches from travel height.

We suggest you call the manufacturer of the RV or AC – or both – to see if they can provide any guidance. Input from other RVers welcome.

AC in Summer Heat

by Mike (Mexia, TX)

Question: I live in Texas and we get pretty hot down here around July and August. I have a 33 ft RV and it has only 1 AC unit. It is already 105 degrees and the AC runs continuously to try to keep up. Any suggestion about supplementing my cooling. I’ve already added 2 fans.

Answer: We assume you already have the shades, windows and any vents closed. You can also buy vent shades if you have vents that let in a lot of heat. Insulated curtains or reflective windshield shades may also help.

If possible, try to find some shade to park under. Or if it makes sense for your situation, build a covered RV carport to park under.

It may not be feasible, but perhaps there is a way to supplement your power source to add another air conditioner.

And if your circumstances permit, consider going somewhere cooler for the summer months.

We invite comments from anyone with other ideas.

Jun 30, 2015 Insulating against summer heat in Texas.
by: Anonymous

We also live in Texas. I went to Home Depot and purchased a couple of sheets of 4 X 8 insulated wall insulation. The kind they use in home construction. Silver foil on one side white on the other with yellow foam between. I cut a piece for each window and ceiling vent. They reflect all of the sun back out, insulate against AC loss and they keep it dark and cool inside. You can sleep early or late.

Make the ceiling vent piece with a small cutout in one corner so you can pull it out for showering. Cover the edges on this one with duct tape to keep the foam from flaking. Works great. I use it in my homes windows too to keep the power bill down in winter and summer. Saves your blinds and curtains from fading also.

Nov 04, 2013 Dehumidifier
by: Anonymous

When I workamped in South Padre Island several of the RVers put a portable dehumidifier in their rigs and said it helped a lot.

Air Conditioning Not Working

by Lori S. (Pascagoula, MS)

Question: We checked all breakers and GFI and still no AC. Fan will run and you can hear the compressor try to come on, but it will not. We are first time RVers. We got it home and still no AC – what are we doing wrong? We are so frustrated. We even had an electrician put in a 30 amp breaker so we could get it ready and have the AC going. Please help. 2013 Coachmen Freedom Express 28rld.

Answer: You are not doing anything wrong. The most likely source of your problem is a bad capacitor in the AC unit. This is a cheap and easy fix if you do it yourself (order a new capacitor and install it). However, have you tried going back to the manufacturer? Since you have a 2013 it seems your RV and components should still be under warranty. Even new rigs have failures – hopefully you are still under warranty.

If you are not under warranty, you can try to fix it yourself or take the RV in to have the air conditioning fixed. But even if your warranty is over, we suggest you call Coachmen and/or the AC manufacturer for help. You shouldn’t have this type of problem on such a new rig – they should at least be able to offer some technical assistance.

All the best – please let us know the outcome.

Air Conditioning

by Doug (Forest, OH)

Question: My camper air conditioning will run for a while, then it starts kicking the air conditioning off for a short time, then it comes right back on, then goes right back off. What is the problem?

Answer: Your problem is called short cycling. There could be a number of things that can cause this problem, from a misplaced thermostat to a bad control board.

Without knowing the details of your specific troubles, here are the most common causes that might help you troubleshoot:

  • Thermostat too close to an ac vent
  • Your compressor coils could be freezing up due to low ambient temperature
  • Low power to the control board – 120 volts or 12 volt (your ac uses both)
  • Intermittent problem with the start capacitor
  • Bad control board
  • Bad thermistor

You should try to consult your ac owners manual for help. If you are unable to resolve this on your own, contact the manufacturer of the AC or a qualified RV air conditioner repair facility. We have had success finding mobile repair people.

Other input welcome and best of luck with your AC problem.

Mar 24, 2016 Have to manually turn fan to get to work
by: Anonymous

I have to manually turn fan to get ac to work then if I turn it off, I have to restart the same way. What could this be?

Feb 16, 2016 Re AC issue
by: Anonymous

In order to offer any assistance, would need more info. It would be helpful to know the type of A/C unit, the make/model of the thermostat and whether or not this is a new problem. Were the A/C and furnace were functioning properly before?

Feb 14, 2016 a/c
by: Joe Pena

I have a Jayco 5th wheel when I turn on the a/c the compressor tries to turn on after a few seconds it goes out and the furnace kicks on.

Sep 30, 2015 Loose A/C motor
by: Anonymous

Barrie, have you tried to remove the A/C shroud so you can see inside the metal housing and any freon lines. My guess is that it would be OK to use the self tapping screws to attach the motor’s L brackets to the metal shroud. Another solution would be to get someone to tack weld the brackets back in place. Best of luck with your repair.

Sep 27, 2015 loose ac motor
by: Barrie

The ac motor on my 1989 Cobra Sierra has a loose motor which causes the fan blades to hit the shroud.I have tried epoxy, zip ties and wood blocks that all came loose.The motor comes out of a large metal housing and I have considered screwing self tapping 1/2 in. metal screws into L brackets connecting the motor to the metal housing.My fear is I could damage the motor or puncture a freon conduit that may be inside the metal housing.Any suggestions?

Jul 10, 2015 Ac turns off once a month
by: Cynthia C

Question: my fifth wheel air conditioner turns off once a month… after a day and half it turns on and stays on. I have a electrician checked on it but doesn’t know the problem. Does anyone had this problem or knows what’s going on?

Jul 06, 2015 AC won’t turn on unless turn to 50 degrees
by: Bryan R

I tried to use my AC this weekend and when I turned it on and put the theromsat to 70 it wouldn’t turn the unit on. I put it down to 50 degrees and then it would turn on and run. Could the theromsat be bad? It worked a couple of weekends ago with no problems.

Apr 16, 2015 antifreeze leaking from air conditioner
by: Margaret

I have a Cyclone toy hauler. I had everything winterized. I went in to inspect through the winter and the pink anitfreeze has run – leaked through an outlet under the cupboards and down the wall onto the counter. I checked inside the cupboard and there is no fluid. Not sure but I’m thinking it has something to do with the air conditioner. Any suggestions where it could be coming from and how to fix it?

May 26, 2014 AC short cycling
by: b j

You have a freon leak and the under-pressured high side and suction pressures will cause the evaporator to drop below freezing and open the frost switch which shuts down the unit. Check your exit temps and pressures.
Best idea:
If you can afford an RV, you can probably afford a a/c repair by a professional. If not, take out a window and stick in a $200 window unit.