Troubleshooting my roofmounted A/C, Air Conditioner

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jasonblu

Member
Joined
Jul 7, 2010
Posts
15
Hi again all.

I am having trouble with my A/C unit. If anyone could help me, I would greatly appreciate it.

While plugged into shore power...

SETTINGS:
Heat/Cool Switch set to: COOL
Fan Set to: ON and/or AUTO
Thermostat: Slid to coldest setting

SYMPTOMS:
Fan never comes on, regardless of AUTO or ON setting.
Sliding thermostat gives a satisfying "click" sound when transitions colder than current temp letting you know its trying to turn the unit on.
Compressor "TRIES" to come on. You hear a "humming/groaning" sound, and sort of "swishing" sound, but no cold air blows out of vents (obviously, since fan never kicks on).
Then, after you turn it off and on, SOMETIMES, the compressor wont come on at all. I have to reset the 20A breaker and wait a while before being able to get the compressor to at least hum and groan again.

WHAT I HAVE TRIED ALREADY:
No blown fuses in main breaker panel.
No tripped breakers in main breaker panel.

ANY IDEAS??

If its of any importance, my trailer is a 2005 Thor America 31-UKS. Has only 1 roof mounted AC unit that has hardly ever been used.

Thanks All! :D



 
The "humming/groaning" sound may mean the compressor is running okay because turning it off then back on pops a breaker.  That would mean the compressor has built up pressure and can't overcome it to restart and draws excessive current - thus "pop", a typical occurrence.  As for the fan, it should come on when set to "On" and should come on any time the compressor runs.  My guess is a bad fan motor or motor wiring.  But, it could be as simple as a big dirt dauber nest in it.  Open it up and see if the fan turns freely by hand.
 
Great suggestions. Thanks. I will check that out. I am assuming I can do this by going up on the roof and removing the plastic cover - fan will be visible and accessible from there?

One item of clarification...the unit never actually *trips* the circuit breaker. But turning the unit off at the breaker *sometimes* gets it to at least "hum/groan". It's strange, I know.
 
Yes to your question of going up on the roof and removing the plastic cover.  You will see the motor and the cooling fan for the condenser coils.  The fan for the air in the trailer is on the other end of the motor.  The motor has a shaft out each end.  Make sure the power is off if you have your hand in there.
 
Based on my Coleman AC, with the shroud off you should see a metal plate on the side that can be removed to expose a couple of capacitors that are used to start the compressor and the fan.
They tend to fail but usually do cause a breaker to open. Still it might be worth removing them and doing an ohmmeter check to see if they have a high resistance (infinite after a quick low resistance) as they should.
 
It is much better to check the capacitors with a capacitor tester, registered in microfarads.  These are a high possibility that one or even both are bad.  And there is such thing as a 'hard start kit'.  This is a capacitor and start relay in one package, and is frequently used to remedy problems such as yours.  These are inexpensive and easy to install, but usually have to be bought at HVAC supply stores.

 
So I went up on the roof and removed the cover. found the fan "stuck" from lack of-use I suppose. I spun it manually but it still wouldnt turn. It took leaving it on and running back up there and pushing it with a rod. That got it spinning - now it seems to be working fine. Blows cold. Caps must have been good after all. THANKS EVERYONE FOR THEIR ASSISTANCE!  :)

Followup question - is there a easy way to lubricate these fans? The spindle that the rubber fan blade was attached to is dark with corrosion. Crazy seeing that this unit is only 6 years old!
 
My choice for something like that is Seafoam's Deep Creep to penetrate.  Corrosion Block works well to keep metal from starting to corrode.
 
Natetheskate said:
It is much better to check the capacitors with a capacitor tester, registered in microfarads.  These are a high possibility that one or even both are bad.  And there is such thing as a 'hard start kit'.  This is a capacitor and start relay in one package, and is frequently used to remedy problems such as yours.  These are inexpensive and easy to install, but usually have to be bought at HVAC supply stores.
Click to expand...

I agree...start capacitor is very common failure. ..and start relay when OAT is really hot. I carry a spare kit all the time..replaced two since I have had the MH. I have repaired fellow campers too with my spares. Failure most probable at parks with poor voltage (less than 110V) at the hookup..and every one is running A/cs..

Most RV supplys have the Hard Start Kits for Coleman A/Cs. (22-26 dollars) or search on line for "hard start kit"
 
New guy here. I have been searching your site in hopes of finding an answer to my problem with my coleman. I am having similar problems as this gentleman did. My rooftop fan works on low and high and the heat strip works, but as soon as the selector is switched to ac it kicks out the breaker every time. There is nothing blocking any thing as far as I can see. Would this happen if the compressor needs recharged? If the compressor is locked up is it worth getting a new one or just replacing the whole unit, it is quite an old one. Thanks to anyone who can shed some light on my problem.
 
I personally would replace the whole unit if it is more han 5 years old. That being said, if the heat strip and everything else is in good shape I might expore the cost to repair vs replace.
 
Hi there,
I'm having the same issue that was mentioned in here earlier. I have a Coleman rooftop ac on a camper I recently bought. The fan works fine on low and high, but the moment I turn the knob to ac, the breaker trips. Can this be caused by a bad capacitor? Should I try replacing it? The unit seems to be in good shape other than this issue.
Thanks.

G
 
Breaker tripping is rare from a run capacitor unless it has completely exploded and spewed all the internal oil everywhere. You will be able to see this easily if the capacitor has exploded. A capacitor can fail without the previous statement and they usually appear swollen.
With the breaker off look around the unit and compressor terminals for burnt wires etc. I don't know how experienced you are with wiring but removing the compressor terminal box is easy(with power off) and see if anything looks melted or burnt.
I hope your compressor is ok but from the sound of it you may have a shorted or grounded compressor if the wires in the terminal block look ok.
If that is the case a new AC would be your best route if the camper is over 5 years old. IMHO
 
jasonblu said:
So I went up on the roof and removed the cover. found the fan "stuck" from lack of-use I suppose. I spun it manually but it still wouldnt turn. It took leaving it on and running back up there and pushing it with a rod. That got it spinning - now it seems to be working fine. Blows cold. Caps must have been good after all. THANKS EVERYONE FOR THEIR ASSISTANCE!  :)

Followup question - is there a easy way to lubricate these fans? The spindle that the rubber fan blade was attached to is dark with corrosion. Crazy seeing that this unit is only 6 years old!
Click to expand...

Not using very frequently will dry out the sleave bearings in these units. Adding some lubricant on the shaft where the bearings seat on the shaft will add some life to your dual shaft fan motor. I would also turn on at least once a week for 10 minutes or so if not freezing temps outside.
Just noticed how old that post was but the advice still holds true :)
 
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