Troubleshooting and Maintaining Your RV’s Air Conditioner
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.
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
A Bad Compressor Isn't Usually Worth Fixing
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
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
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 
These fin combs are very inexpensive and may be used many times in the future on both RV and home AC coil fins.
Straighten out those bent coil fins and increase the efficiency of your A/C unit.
Maintaining the AC Fan Motor
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.
Related
Comments
AUTHORJim, the drain should be easily seen if the unit has one. Many newer ACs don't use one. Are you sure it's not simply dirty coils causing the problem?
Randy
how to un-Clog Air conditioner drain line
- AUTHOR
Jeramoran, good news and thanks for relating the solution to your problem. :)
Randy
- AUTHOR
Art, this sounds lime a control board problem unless the thermostat is bad.
Randy
Update on post from last week. We are up and running. The in line fuse auto reset was bad. We replaced it. Finally figured out battery black and white negative and both reds positive. EVERYTHING works. Yippie.
Thanks for the great information !
Randy I have a Coleman Mach roof mount w ceiling controls. My issue I have the fan stop after a few moments of use, regardless of speeds. I have replaced both capacitors and even the ceiling controls. I hear the compressor kick on. sometimes the speed of the ceiling fan will fluctuate. After it fails I shut it down to off, wait a cpl mins and restart. It again will run for a few mins and fail. I have a 2010 Jayco 19ft hybrid. The unit over the years as had very light use on the AC. What else could it be?
Thanks randy, good was thinking the same thing. I wanted second opinion before I spend $$$.
- AUTHOR
Ribright, if you're sure the stat is operating properly then you may have an issue with the control board.
Randy
- AUTHOR
Justin, assuming the fan normally cuts off when the compressor stops, the only thing left is the control board which receives the signal from the stat.
Randy
Filters and condenser coils are pristine. New unit (2016). My AC blows ambient air both on AC and when heat pump is selected. I have a Dometic single area thermostat with fan, cool, furnace and heat pump as it's selections. Compressor comes on and off as it should but air temp never changes.
Roof AC blower will not stop running. The unit is from 2012. It will momentarily turn off while compressor turns off and on but go back running. I’ve replaced thermostat. And it is set to auto.
- AUTHOR
Good news, Jeramoran! :)
Randy
We may have found the problem. The fuse link at battery .we took it off to clean since it was rusted one of the posts come off and was not making contact.
Taking it home to find replacement. We will keep everybody posted.
- AUTHOR
Jeramoran. first check the capacitors in the AC. You may have a weak cap causing the overload.
Randy
Help! We have 29 ft travel trailer fourwinds . Ac and Refrigerator wont stay on consistently its plugged into shore line. Seems like when compressor kicks in it shuts back down.
We replaced battery and yep forgot to take pictures of how it was connected.Our slide is working now
Not sure if it's a converter problem.
- AUTHOR
Terri, this may be a control board issue. Try powering off again and see if the code resets.
Randy
I have an E7 error code showing on my fifth wheel control panel for zone1 only. Zone 2 is working fine. We had to power off some things earlier and then back on. If anyone can make a suggestion I would appreciate it.
- AUTHOR
Wayne, more than likely you have a bad door gasket if a drain isn't visible in the outer fridge access door.
Randy
- AUTHOR
Matt, have all caps checked as it only takes one weak cap to cause this problem.
Randy
Is there a drain hose on all RV refrigerator my Tioga arrow when running frig it will get carpet wet can’t find the water ven line can u help
Hi Randy,
I'm glad I found your website, thanks for all of this usefull info. I have a 2001 coleman popup with a 13,500 BTU rooftop AC, that I've never maintained. The camper has been garaged its whole life. The AC works ok and I recently bought a Champion 3400/3100 Watt generator. The gen will start the unit initially, but overloads when I dial the thermostat warm then cool. It seems both the running fan motor and starting compressor are too much. I replaced the hard start capacitor, but no change in performance. Thinking of testing the fan capacitor next, and oiling. Thoughts?
Thanks again.
- AUTHOR
Jimmy, sounds like either the thermostat or the control board is bad.
Randy
The ac unit on our 2013 heartland cyclone kicks on and off and is reading the E5.
- AUTHOR
Patricia, if you haven't cleaned the coils yet then you need to do so. You also need to check the capacitors as one of them may be weak or bad.
Randy
The AC keeps tripping the breaker, 90% if the time at night (after 8 pm). We dont change the temp. We are work camping and we are the only tt hear. Any ideas?
- AUTHOR
The coil behind the filter will get clogged over the years more so than the outside coil. This can cause the compressor to overheat because the fan cannot intake and exhaust the hot air easily.
Randy
No, I haven't, Randy. The outside coils look fine, but I have not taken the metal shroud off to look at the other ones. I will try and do that in the next day or two.
- AUTHOR
Roy, have you cleaned the coils yet?
Randy
Randy, I just checked the capacitors with my multimeter; they all checked out fine. Now, I've noticed something about this problem: it seems like when the humidity AND the outside temps are high, the problem with this compressor shutting off and on becomes pronounced. Then, when the temps come down a bit, like at nighttime, the compressor seems to work normally.
I did not replace any of the capacitors.
This is not a scientific observation because the problem just began yesterday, but it seems to be yet another piece of evidence of why this might be happening. Any ideas?
Thanks again.
Roy Spears
Thanks, Randy.
- AUTHOR
Roy, you can use a multimeter set on ohms to check the capacitors. When the probes are applied to the terminals you should get a random number decreasing in value if the cap is good. Otherwise, the cap is weak or bad.
Randy
Randy, all of a sudden my Coleman Mach ac unit on my RV is doing something it has never done before: while the unit is running, the compressor now kicks off and on. I usually keep the unit on "Auto," and never before has the compressor acted this way. And the compressor seems to run for a few minutes, with the fan continually going, then the compressor shuts off, the fan continues, and then the compressor kicks back on. When the temperature in the RV reaches what I set it to on the thermostat, everything shuts off like it normally does.
Does this sound like a capacitor problem? I just recently replaced the motor and it has been working flawlessly until just a couple of hours ago.
Roy Speas
- AUTHOR
David, I hesitate to advise you this as the control board may not be the one needed for a heat strip. Normally there would be a connector already installed if the control board was wired for it.
Randy
Well Randy, I have another dilemma.
I decided to invest in the optional heat strip despite all the reasons not to. Upon fitting I found that my unit didn't have the two pin connector for the strip although I do have a heat/cool thermostat.
Any ideas how to wire this without the missing 'heat ready' connectors?
- AUTHOR
David, pleased to hear this. Sorry I didn't have solution for you. I'll keep the solution in mind for others with a similar problem. Thanks!
Randy
Figured it out, thanks Randy. the B- terminal was the -12V back to the stat. Doubled up to that connex & I'm back in business. Thanks for the reply!
- AUTHOR
David, I don't have a wiring diagram for this unit. Look online at the Coleman site and there may be a diagram or someone who can help you. Sorry! Does the unit still work normally? If so it may be an extra ground for the board or other electrical component.
Randy
I have a Coleman Mach 3 (8000 series). I decided to inspect the coils and, when I pulled back the metal cover, a blue/white striped wire came free. The other end is attached to the a/c chassis so I'm assuming it's a 12v return wire.
I cannot find where it got dislodged from. Any clues?
- AUTHOR
Bert, this sounds like a low Freon charge. Have cleaned the coils yet? If not, do so and see if this helps any. You might also visually inspect the AC to see if there's an oily spot where the Freon leaked out.
Randy
AC runs - but blows cool, not cold - will not keep camper cool during the day with temps in the 90’s, but did manage to cool down to 75 last night. Did cycle on and off during the night, but runs continuously during the day.
- AUTHOR
Skeeter, more than likely the thermostat. If not, the control board is all that's left.
Randy
Thanks Randy. I cant set it manually the unit only has ac/heat on off no temp control.
- AUTHOR
"How can", to see what a capacitor looks like go on Amazon and look for RV AC capacitors. They are located under the shroud and you will see them near where the electronic control board is.
Randy
How do i locate the capacitors on my travel trailors ac unit?
- AUTHOR
Skeeter, it may be either the thermostat, the remote, or the control board. I'd think you could set it manually instead of using the remote.
Randy
My Carrier ac has a remote and I cant change the temperature setting at all its stuck on 75. Could it be something with the unit or do I just need a new remote?
- AUTHOR
Wesley, apparently the original wiring was defective or else the breaker controlling the unit is bad.
Randy
I have a rear ac unit , it has the 12 volt dc but not 120 volt ac? Its on a 1994 pace arrow with 2 roof top units, 1 works and the other doesnt? I used a extension cord and wired it in and it works fine like that
- AUTHOR
Charlie, the control board controls everything, including the fan and compressor. If the stat checks out okay, then there's nothing left but the control board to cause this issue.
Randy
- AUTHOR
Haller, this may be either the thermostat or the control board. Check the stat first.
Randy
Hey, Randy. Thanks for the advice below (2 weeks back) and sorry for the delay in responding. You said "this could also be the stat or control board." I just want to clarify: The thermostat seems to function fine in low cool (rotating dial on the unit). I guess that leaves control board or the motor. Is it possible that the compressor could come on, the motor doesn't run AND it is the control board? Seems like if it is the control board, nothing would happen (including the compressor). If you have any more clarifying remarks, let me know. Thanks a million!!!
I have a 2018 Jayco with a Dometic ac unit. When running the ac in automatic mode. The unit tries to shut off when it reaches right temperature but kicks right back on.
- AUTHOR
Zipptogo--Yes the stat could be the problem, but it may also be the control board. Check the stat first.
Randy
Have a roof unit with dual control stat on the wall . Plugged up earlier before work to an outside outlet at my home place and when I returned home I must have lost power sometime during day . That said my stat temp says 99 but off . I turn it on and the a/c unit never made a peep . The stat read automatically at 37 and I could not adjust the stat but yet no power. Everything else in RV operates just fine . All fuses are good and no breakers tripped. I’m thinking stat problem hopefully but need guidance.
Good Day,
I am looking at a 2012 class A and I was wondering if I were to put a thermometer at the vent about what temp should I expect? The MH is in So Calif and the outside temp is 107. It seemed to me that air was warm, but at 107 outside....... I have instant thermometer and infrared one I am taking with me to check it tomorrow.
- AUTHOR
Clyde, you may have a weak compressor capacitor. Check this first.
Randy
Hey Randy
I got back up here to WI to My rv last night...
Left thermostat on “auto” at around 70 degrees...
It was 94 degrees in the rv...
It’s blowing hot...when I “reset” the a/c by removing shore power,it’ll blow nice & cold for a couple hours..
Then “loses it’s cool”
- AUTHOR
Glad to help, Grandpa! :)
Randy
Follow up on my Dometic AC. I did find a few mud dauber nests, but none in the squirrel cage. The big one that was causing the problem was on one of the fan blades. Not what I was expecting. Thanks for your help.
Thanks Randy will keep ypu posted
- AUTHOR
Sammy, anything is possible with a new AC unit, no matter the make. You'll need to get in touch with a Dometic Rep to avoid voiding the warranty by doing anything to fix it yourself.
Randy
New dometic penguin ll instaled Wednesday fan runs about 2and 1half min. Comp. Runs another 3 min could they have used the wrong board i have a 5 button thermostat
- AUTHOR
Cool, Clyde!
Randy
Randy
Will do...
I’m waiting on a new capacitor now.
I’ll post results after I install.
- AUTHOR
Clyde, if the new cap doesn't solve the problem, it's either the thermostat or the control board. Start with checking the stat before replacing the control board.
Randy
Hello
Great tech advice!
I have a Coleman/Airexcel roof ducted unit...
Fan motor runs,however the condenser doesn’t seem to...
I’ve had it plugged into a 30 amp post @ campsite the past few months..its a 2013 model Itasca.
Wall mounted digital “Coleman-Mach” thermostat.
It only blew warm air the last 24 hours.
I got the good aresol cleaner from Ace Hardware...and cleaned.
It still only blew warm air,and thermostat was “stuck” on “80”
The “auto” function doesn’t comply...
I unplugged everything and attempted a reset. When I turned it back on it’s blowing cold...but only after I turn setting down to 65 or below.
And the auto function still doesn’t seem to kick in the air..
I ordered a new capacitor (running cap)
But haven’t received it yet...
What do You think?
- AUTHOR
Marty, may be a bad transfer switch. I assume you've checked the power to the 110 volt panel to see if power from the GEN is getting there?
Randy
- AUTHOR
Wayne, yes you can order a new stat online. It may be the stat or the control board causing the problem.
Randy
- AUTHOR
Donald Robbins--Try using a good spray no-rinse coil cleaner on both evaporator and condenser coils. You can find it at ACE Hardware or on Amazon.
Randy
- AUTHOR
Michael Davis, I've ran into this problem before and it was a weak compressor capacitor. Try changing the cap and see if it solves the problem.
Randy
- AUTHOR
Charlie O--this could also be a bad control board or the thermostat. Check the stat first.
Randy
When I start the onboard generator nothing inside works I can hook power cord to an outside generator and everything works fine any idea what it might be
My RV AC WILL NOT shut down it’s runs and cools but the thermostat on the ac unit doesn’t control the temp anymore it’s not wall mounted it’s on the ac unit itself is there a way to replace it
I just got back from a weekend of rving. The rooftop A/C cools fine but it does not remove the humidity from our rv. I had readings from 70% to 90% humidity. VERY uncomfortable. Any idea what could be causing this?
Here is the issue that I am having. (I have looked through the comments to avoid asking a repeat question but can’t find my exact issue). I have a 2009 Palomino Puma 19fs travel trailer with a 13,500 btu Dometic ac unit on a 20 amp breaker (30 amp main) on a tandem single pole breaker with the main. When connected to the shore power both at home 20 amp 110v plug and at 50 amp campsites the ac runs fine. When connected to my generator (5000 starting watt 3500 running watts Briggs and Stratton)the AC will run for a while and then the breaker will trip. Also the main camper power will go off then on real fast but the main will not trip.( My TV will turn off then back on real quick). The breaker for the AC will not reset until I turn the AC off at the thermostat. When I turn the AC back on the generator bogs way down. The AC will run for a while then trip at random times, even when nothing else is on. Also sometimes the AC will run for several hours and nothing or trip 4 or 5 times in an hour. First I thought it was the generator so I hooked up to a 7000watt 5250 running watt generator and it would do the exact same thing, this time it would also trip the generator main breaker as well. What do you think the problem is? Capacitor? Breaker? RV Converter? Or new AC unit? Thank you
Randy, one more piece of info to go with my previous post: When I select "high cool," I can hear the condenser running, but the fan motor does not run. Thank you for any advice you can provide!
Randy, my high fan and high cool modes on my rooftop AC have failed. The unit still cools well on the low setting and the low fan works fine. Basically, I was using the unit while camping in high mode, switched it off briefly and when I turned it back on it wouldn't work in high mode anymore Your article suggests this is a motor problem. I'm wondering if it is elsewhere. What do you think? This is a 2014 Jayco with AC model number 48254C966.
- AUTHOR
Grandpa--yes this is a bit of a bad yaw.
Randy
I have already found two wasp nests, received one wasp sting and a few hints of mud daubers but have not yet looked in the cage. I will do so first. I do hope that you are right, but the fan is turning at a normal pace and the shaft is in at least a one inch diameter yaw and that seems like a lot to me. Thanks for the response and I will let you know what I find.
- AUTHOR
Grandpa RVer, yes it's not to difficult to change the fan motor if it's bad. Did you check to be sure there was no mud dauber nest on the squirrel cage fan? This happens more often than you'd imagine.
Randy
I have a Dometic Duo Therm AC unit that is 10 years old. Never had any issues. Just turned it on and it is vibrating badly. Still cools and fan blows. I removed the shroud and the fan shaft is not secure. Should I try replacing the fan motor? Seems to be a fairly simple job.
- AUTHOR
Shannon, first check--or have the capacitors checked--to see if they're bad. You can do this with a digital multimeter if you have one.
Randy
- AUTHOR
Sandor, not too difficult to change the fan motor out, but a bit time consuming.
Randy
New to the rv life. I have a 2016 Winnebago spider toy hauler. Dometec ac unit. Has power to thermostat but nothing turns on. I bought this coach as is with some electrical work needed but as a single mother, electrical stuff is not in my resume, but every other manly job I got mastered! lol help! Please it's southern Nevada heat high today 108 degrees!
hey randy thanks for the reply. I changed capacitors and had them checked everything is ok. Still doesnt work. Time for a new fan motor and how hard is it to change? Thanks
- AUTHOR
Stanley, the power for the thermostat comes from the 12 volt power panel in some manner. The same goes for the thermostats in the fridge and H/W heater. Check the fuses or breakers in the 12 volt DC panel first.
Randy
Correct, one thermostat controls both units. This is the rj11 "phone cable" type units. I do not have 12v at zone 2. Where does it get its 12v signal from? When i apply 12v to the black and red wire, it powers up. But those wires have never been used before. And yes, both units used to work. Thanks for your quick response......
- AUTHOR
Stanley, if you only have one thermostat, then yes, both units are controlled by it.
Randy
I dont seem to have 12v to Zone 2 ac in my rv. Is the 12vdc fed from the zone 1 ac?
- AUTHOR
Sandor, I suggest you look on Amazon for different capacitors to see what your AC uses for the fan motor. This way you'll know what to look for beneath the shroud. About $25 in most cases and easy to change. Make sure you don't touch the terminals until you discharge the cap with an insulated screwdriver or you may get shocked.
Randy
HI Randy my 2007 mandalay valencia deisel pusher has a main ac unit has stopped working. It makes a humming noise and trips the breaker. I opened the unit and see the squirel cage is not spinning. I pushed it with my hand and it started spinning then it would stop. I tried it again and same thing would happen. If it is the capicitor where and how do I change it. Thanks
- AUTHOR
Greg, may be a restriction in the system or low on Freon.
Randy
Dometic 15k machine - compressor cuts on - blows hot air only - I'm thinking low or out of freon.
- AUTHOR
Josh, check the capacitors first. A bad cap can cause this problem.
Randy
Hi Randy, our 2018 MPG has two ac units. The main one is working fine but when I hooked it up today the second unit is turning on. The thermostat is working but it does nothing when I turn on the ac. I tried the fan on auto, high and low and it doesn't do anything. It has been working fine until today. They are dometic ac units. Any ideas?
- AUTHOR
ktutt, you'll have to look on Amazon for the model of your AC and which Capacitor you need.
Randy
Any part number for new capacitor for compressor on Dometic roof ac.
- AUTHOR
Howard, yes it could be a bad capacitor. Easy to change out and around $25 or so.
Randy
My coleman mach ducted system only blows warm air .. less than 3 years old sit up at the beach .. can it be a capacitor issue ?
- AUTHOR
Bob, this may be a control board problem if everything else checks out.
Randy
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