How to Troubleshoot, Service, and Repair a Motorhome or Camper Travel Trailer Rooftop RV Air Conditioner AC. FAQs
The Importance of RV AC Maintenance
The rooftop air conditioners used on motorhomes are made to give many years of dependable cooling efficiency. But in order for the AC to operate dependably each season, it is necessary to keep the rooftop AC unit on your motorhome clean and properly maintained.
Occasionally the motorhome rooftop AC needs repairing and this article will assist you in knowing which parts of your RV AC to replace or service.These repair and maintenance tips are very simple to follow, even for those with less than good hands-on experience.
If you are unfamiliar with how a motorhome air conditioning system works, this article will help you understand which parts of the motorhome rooftop air conditioner unit to check, service, and repair.
Condenser and Evaporator Coil Maintenance
Roof air conditioning units are the same as ones used on other types of RV campers such as travel trailers and pop-up campers. Your motorhome AC system may have one or two units to help keep the camper cold, or warm if the RV AC units have optional heat elements. These repair and maintenance procedures are identical for all types of the aforementioned campers.
After a few seasons of use, it isn’t unusual for the AC unit(s) to not cool the motorhome as quickly or as efficiently as it once did. Even though you have kept the filters clean on a regular basis, 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 by unscrewing the four bolts securing it to the RV AC unit itself.
Accessing the AC coils
How To Clean The RV AC Coils
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.
A good wet/dry Shop Vac will help to keep you from making a big mess during the cleaning regimen.
Although regular household cleaners may clean the coils to a certain extent, AC coil cleaners made especially for the purpose, like the ZEP product below, will remove the grime build-up much more efficiently and will not harm the coils themselves.
Follow the instructions carefully for the best results and use the Shop-Vac to 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.
Cleaning Your RV AC Coils
A/C Coil Fin Comb
Straighten out those bent coil fins and increase the efficiency of your A/C unit.
While the RV AC shroud is removed, it is a good time to service the fan motor and clean the fans themselves. 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 in it there will be oiling ports at each end of the motor. It may be necessary to remove the top metal sheeting from over the fan motor to access the bearing oiling ports.
A few sheet metal screws will have to be removed to allow you access to the bearing ports add oil to the bearings.
If no oil ports are evident, then your rooftop AC unit has sleeves instead of bearings. You may still oil the shaft at the point where the sleeves are contained in the fan motor housing. The oil will seep inside and help the fan motor last much longer.
A fan motor with sleeves cannot be rebuilt economically, as can the bearing models, and must be replaced with a new one. Check the ads below to find the right fan motor for your RV AC.
Maintaining the AC Fan Motor
How To Replace A Motorhome AC Fan Motor
If your AC fan motor is slow to start even after oiling, or needs a nudge to get it going, it will need rebuilding or replacement with a new one.
As stated previously, a bearing model fan motor may be rebuilt fairly cheaply and will last for many more years. But not so a sleeved bearing AC fan motor.
If your unit seems to be in pretty good shape a new AC fan motor may be ordered to fit your particular RV AC unit.
Check out the links on this page to find the type of fan motor you need to replace your model Click on the ads to look further on the Amazon site if you do not see your model of fan motor. There are many sizes and models to choose from.
Replacement of the AC fan motor is a simple job with only a few tools required for the project. Mark the wire colors before removing the fan motor if the connection isn’t a simple plug-in type electrical connection.
Test the new RV AC fan motor before replacing the AC shroud to check for proper alignment and fan clearance.
Replacement RV Rooftop AC
Removing and Replacing the Fan Motor
RV AC Capacitor Replacement
If the fan or compressor fails to start and the AC unit merely hums or trips a breaker, it is possible the starting capacitor is malfunctioning. The capacitor stores electricity to give both the fan motor and the compressor an extra boost when the RV AC unit first starts. It is not unusual for this item to go bad.
The capacitor is easily replaced in the event it has gone bad. Note the wiring before removing the old AC capacitor and install the new capacitor in the same manner. Your AC unit should now start and run fine. Check the required voltage and model numbers on the new AC capacitor when ordering a new one.
RV AC Compressor Problems
If, after determining the switches, capacitor, and relays are not at fault, the RV AC compressor fails to operate correctly 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 be too expensive to repair in most cases. Under normal circumstances the compressor will last much longer than the warranty covers.
The thermostat and switches may be purchased online by finding the correct model and serial numbers before ordering the new parts. These items w\are very easily replaced in most cases. Pay attention to the wiring connections as always when replacing these electrical components.
RV AC Protective Covers for Motorhomes
Protect Your Motorhome AC Unit In The Off Season
Your motorhome AC unit should give you many seasons of dependable operation if serviced annually. The use of a cover for the RV AC unit is highly recommended during the times when the motorhome is not in use.
These inexpensive RV AC covers protect the unit from being exposed to moisture, extreme cold or hot temperatures, and debris from storms, birds and insects. They will more than pay for their cost over time.
If your RV AC unit needs 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. Don’t be afraid to try these service tips yourself. You will learn much about these wonderful RV air conditioners.
Related
Comments
- Author
Carol, it may be either the thermostat or the control board. I'd check the thermostat first.
Randy
- Author
Do you mean the awning, Red?
Randy
- Author
Keith, it's possible the heating element is burned out. An easy replacement job, if so.
Randy
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!
how do I troubleshoot my owning
My duo therm unit does not blow hot air. Any ideas
- Author
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
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?
- Author
Tony, it could be the thermostat or the control board. Check the thermostat first.
Randy
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
- Author
Your wife may be right, James. A new capacitor is cheap and worth a try before replacing the fan.
Randy
- Author
Chris, check the compressor capacitor as this may be the problem.
Randy
- Author
Ian, check or replace the capacitors first.
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
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.
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.
- Author
It does indeed seem the thermostat is faulty, Mike.
Randy
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.
- Author
John, it could be a bad capacitor. An inexpensive and easy replacement in most cases.
Randy
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
- Author
Brian, a weak capacitor will cause this problem, especially when powered by a generator.
Randy
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
- Author
Wade, more than likely it's the thermostat or the control board causing the problem. Have you checked the thermostat voltage yet?
Randy
compressor running with thermostat turned off
- Author
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
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
- Author
Rodney, try replacing the fan capacitor and see if this solves the problem.
Randy
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?
- Author
Jay, sorry the new fan motor didn't fix the problem. Are you sure the breaker is good?
Randy
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.
- Author
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
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.
- Author
Dustin, was it blowing cold air before the cleaning?
Randy
Anyone have any ideas why it won't blow cold air after cleaning?
- Author
Shelly, sounds like low voltage or amperage. What power are you connected to?
Randy
Hi, I have a 2000 Southwind that has 2 ac units.
The units shed and then after a few minutes they keep shedding and slowing lose power to both acs.
They will both work individually but not together properly.
- Author
Mark, it could be a weak breaker, but it could also be a weak capacitor. A cap is cheap and easy to install so I'd try that first.
Randy
I have a Dometic unit which starts and runs normal for about 5 minutes before it trips the AC breaker. It is producing cold air and the motor is working fine. Coils and everything are clean. Could it be a faulty breaker?
- Author
Mark, this may be the capacitor or the compressor. Try replacing the capacitor first--about $20 or so--and if this doesn't solve the problem then the compressor is bad.
Randy
Fan works and it appears there is a power surge as the compressors tries to start. All lights go dim for 3-4 seconds and then returns to normal but no compressor start.
- Author
Tia, yes a system can leak coolant over time. If the compressor is running the thermostat is probably fine.
capacitor works and it sounds like the compressor starts up, however the air does not get cold. Does a system lose coolant or could it maybe be a thermostat?
- Author
Tom, I'd change the capacitor first as it's a cheap--around 20 to 30 dollars--and easy replacement before looking at the compressor or control board. Is it a wall mount thermostat? If so, you need to check it as well.
Randy
I have a 1990 Dometic duotherm rooftop unit. The fan works as it should but the compressor doesn't start. It appears to have only one capacitor for both. Is it possible that the capacitor is at fault or am I looking at a compressor or control board problem.
- Author
E. Wheeler, simply because a capacitor is new doesn't mean it won't fail. If you have a digital bolt meter I can instruct you how to test the capacitors. As for the overhead ducts, if your camper has a few years on it it's possible some of the ducts have collapsed. I've observed this happen more times than I can remember. You might try removing the vent covers and see if you can run a small rod of some sort to see if you vave the same problem. And yes, ants can affect electrical components sometimes.
Randy
- Author
Sorry Debra,I don't understand your question. Care to try again?
Randy
Have a Duo therm unit air or heat want come on checked the fuse on the board in the box in the ac it was blower everyone we replace it it blows
Can bull ants get into your roof ac & affect your operation ?
Fan run & no compressor ?
Hi,We have a 36' Newmar Mountain Aire.
AC was pre-trip professionally serviced & installed new fan blades, & starting capacitor. Ran at home for wks before trip. Dometic 13,000
Went for weekend, all well til woke up 80'F. fan was blowing. . Camp electric 50 amp ck'd ok. What's up?
Is it necessary to keep backup capacitors for your rig ?
Also what volume of air should you expect to flow out of your ac overhead ducts-our high volume flow feels slow & inside cabin feels still & compared to our Holiday Rambler & Airstream Excella ac's of past.
- Author
Pamela, have you tried setting the thermostat to fan only? If so, what happened? Also, it's not rare for a new capacitor to be bad.
Randy
I have a dometic rooftop central ducted AC on my 5th wheel RV. The AC comes on but fan won't come on. I had technican check it out said it was the capacitor. Just replaced it but still the fan won't come on. Unit hums and he said compressor was kicking on and cold air but fan still won't come on. I've checked all fuses and breakers and everything is good there. It was working fine and then it tripped the breaker and fan won't come back on. Any suggestions?
- Author
Daniel, is the compressor coming on or can you tell?
Randy
My fan and a.c unit sounds good but the air is not any cooler when a.c. is on it just makes a little different noise .
- Author
Danny, if the compressor is drawing high amps, then it is toast. Sorry!
Randy
I'm worrking on a coleman rooftop. The compressor ran then I moved the unit off the bench it stopped. drawing high amps.
- Author
Eldon, I'd have the capacitors checked first as they are inexpensive and easy to replace before worrying about the motor.
Randy
I have a coleman mach I believe rooftop ac. yesterday it would not turn on. it would just hum. last night it turned on and ran for several hours then the fan ran slower and slower until it stopped and hummed and would not restart. Capacitor or motor?
- Author
John, this sounds like either a thermostat or control board issue. I'd check the thermostat first.
Randy
When I have the AC on the system flips over to heat mode (reverser value switches). I can watch the system reverse from atop the coach. It's a Dometic 15k heatpump with a 5-button control from 2006. Is this a common problem and what does it mean? I cannot figure out what to do next.
- Author
John, have you checked power from the thermostat to the control board? And are all your 12 volt DC items working correctly?
Randy
Have a carrier air V. Ducted remote. Ac won't come on. Have power to unit checked capaciter changed fuse in control board. Still nothing. Nothing
- Author
.Richard, your coils need cleaning. Get some good no-rinse coil cleaner and this should stop the leaking from the coils.
Randy
my roof mounted air conditioner is dripping water inside the motorhome when in use, how do I correct that ?
- Author
Hi John, yes the unit should lift up easily unless someone has tried to seal around it or applied some type of adhesive to the gasket. Have tried tightening the bolts which compress the gasket yet? If not, I'd try this first before replacing the gasket.
Randy
Hey Randy, I have a 1994 Gulf Stream Conquest. I have it parked on a slight slope with the rear down. When it rains I have a leak over the bed room and have checked out everything except the AC gasket. After taking the shroud bolts out do I just lift the unit up and over or what? Thanks, John
- Author
Faye, apparently the new installation is faulty in some way. Get in touch with whoever installed your new AC as they've probably done something wrong. The unit should recirculate the inside air and not pull in outside air and smoke.
Randy
We have had a new AC unit by Coleman installed in our motor home. Since installing it appears to be pulling air in from outside causing the motor home to fill up with smoke from campfires. Our Carrier did not do this. Is the new unit installed correctly? I didn't think AC units pulled in outside air. I'm very allergic to smoke so this is a problem for me.
- Author
Lee, what are you concerned with? If there's already a inlet for Freon you can always add more.
Randy
It looks like it is low on free on someone has but a tube to add free on in it
- Author
Frank, have the fan capacitor checked or replaced as it may be getting weak. This a relatively inexpensive part to replace and easy to install.
Randy
- Author
Gerald, you need o remove the shroud to see what is causing the noise. It could be bad rubber shock absorbers on the compressor or the fan.
Randy
Hello, I have a cyclone 3800 with a domectic roof top ac unit. Unit is 4 yrs old . Unit works well but occasionally without warning fan will shut off but compressor will stay on. Turn off wait 15 min. Then unit comes back on. Will work good for weeks even months. Then out of the blue fan will stop. Any ideas would help. Thanks Frank
Our RV is a Tiffin Allegro with two rooftop Coleman Mach A/C units (90X4 Series). The motor for the front unit makes a continuous loud noise when running, as if something is rubbing? Any suggestions as to the problem?
- Author
Nick, have you checked the compressor capacitor yet?
Randy
My carrier rv unit ran fine all day but at night the last two nights woke up hot because it wouldn't turn back on for some reason, the units green light was blinking and behind it there was armed light flashing, the only way it seemed to go back on was I turned off power to unit for a minute then when I put back on the green light was solid and turned back on
You can email me at heavyhitters1@live.com
- Author
Miss OJ, I feel your pain! Crooks are everywhere and we must beware of them.
Randy
Randy I'm from Bastrop, La I must have posted on the wrong website. But I did get screwed big time on a camper. He is from Baton Rouge but sells campers in Monroe , la
Thanks
- Author
Travis, check the start/run capacitor for the compressor as it may be getting weak.
Randy
my a/c is a domestic on a 2005 Salem 21' pull trailer...it runs and cools for about an hour then kicks out the breaker any ideas what could be the problem??
- Author
Ronald, check the capacitor as it may be weak, otherwise this sounds like a low Freon charge.
Randy
The compressor keeps short cycling and not staying on it's a duo there 59516 model
- Author
Miss OJ, what state are you from?
BEWARE BEWARE BEWARE John Cavaness of J and A camper sales at 2300 Garrett Road at Pecanland RV park sold me a salvage camper with $13,479.00 damage just labor. About $3000.00 i material. The camper is atotal loss. Damages more than the camper is worth. I asked for a partial refund and he has treated me like crap. I will be picketing sat 7/22 and every day and weekend I can till he makes it fight or takes the camper back. All the campers have visual damage without even going in. Most of my damage was hidden and I did not know about it till I had it pulled to a camper repair to repair what I thought was about $2000.00 in damages not almost $17,000.00. The camper is a total loss. Do not buy from this man or company and come out honk your horns and support me in bringing this bad company down and make sure he doesn't do this to any one else. I will have a hot pink top on to match my hot pink signs. Please come give me your support! Thank You.
- Author
Jim, look on Amazon for a replacement capacitor and you will see what you're looking for. Be careful and not touch the terminal with your bare hands. It's better to cross the terminals with an insulated screwdriver to release any charge still remaining in the cap before removing.
Randy
Thank you for getting back to me. Can you tell me where to fond it?
- Author
Jim, the first thing to do is to check the compressor start/run capacitor. It's an easy and cheap replacement if it's bad. Let me know if this doesn't solve the problem.
Randy
Randy I need help
I have a Dometic 459516 ducted air conditioner with a Dometic control kit#3107541.009 and a Dometic Duo-Therm thermostat. Now for the problem, at the end of last year camping the air conditioner worked but the compressor continually cycled on and off. On for a couple minutes off for 15 seconds back on. These are approximate times. Today is the first time we tries to use it this year and the fan ran but the compressor never kicked on. The thermostat was set to cool, auto, hi. Any ideas I can try? Thank you
- Author
Richard, check the capacitors as they can go bad during periods of idleness.
Randy
Have not used RV in about three months. Tried the RV today. A.C. came on but tripped the breaksr and quit working.
- Author
Thanks for the update, Jay. This may help pthers with similar problems. Let me know how the new fan motor works out.
Randy
Further Update:
Hello Randy...and readers. I received and replaced the second capacitor (43-52 MFD). The breaker still trips. I am wondering if the 3-speed fan may not be spinning fast enough to cool the components, thus causing it to trip the breaker. What are your thoughts? I just ordered another fan motor from Amazon and expect it in the first week of August.
In the meanwhile, I bought a window A/C...so no one is suffering anymore. I removed the smallest window (which is on the slide-out) and installed the A/C there. It's working great. With that unit on, the Dometic A/C has not tripped, but obviously because it doesn't need to turn on much.
After I receive and install the fan motor, I will update you again. I know you and your readers provide answers that others (like myself) depend on.
One thing I would like to share with the followers of your forum:
If you think there is a chance of the A/C's problem being a capacitor, buy a MFD tester. I bought this one for under $16:
https://smile.amazon.com/gp/product/B0036FQ3FW/ref...
I tested my capacitors (my A/C has two) and found that one of them had a higher output than what it should have. The other tested normal but had very minor leakage, so I replaced both.
- Author
Brenda, check the fan start/run capacitor as it may be getting weak.
Randy
Hello, we have Duo-Therm air conditioner that is not working correctly. The compressor is running fine but the fan is intermittent. It runs about 15 minutes and shuts off. Any ideas?
- Author
Which relay. Michael?
Randy
How do I check and replace the relay?
- Author
Fran, are you sure the compressor is running and not merely the fan?
Randy
I have a 2002 dura-thum (sp?) Roof air it runs fine just does not cool what can I do?
- Author
Samuel, have the compressor capacitor checked/replaced as a weak cap will cause this problem.
Randy
Problem I have not seen presented nor solved:
Situation A) When on shore power, RV roof A/C will switch on, the fan will start, but when compressor tries to kick in, the unit will shut down -- but no breakers are tripped.
Situation B) When on generator power, the A/C will switch on, the fan will start, then the compressor will present an amp surge -- and the generator cuts all power to the RV. After about 2 minutes, the generator -- which is still running -- once again provides power to the RV, and no breakers have been tripped.
- Author
Hi Bob, have the compressor start/run capacitor checked.
Randy
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