Air Conditioning problem

jjrbus · June 05, 2007, 08:03:13 PM

My bus conversion hero's are in SC so of course now I have a problem! I have a Dometic 15K (I think) maybe 13K no heat strips. The AC tried to come on but sounded different. It was the fan not running that sounded different. The compressor was trying to start or maybe it was started, hard to tell. I've never heard it without the fan before.
I put the thermostat to off, and the compressor continued to run. I flicked it back and forth three times, but the compressor continued to run. I turned off the circut breaker and the compressor stopped. I reset the breaker with the thermostat off and the compressor came on again still no fan.
I got out my trusty RV repair and maintenance manual but it is really no help. These Ac's are 9 years old with moderate use and my first impulse is to scrap it and buy a new one. But I would hate to have overlooked something simple.
Any thoughts, ideas, suggestions, opinions or wisecracks as always greatly appreciated.

NJT 5573 · June 05, 2007, 08:12:08 PM

Where is your cat? A better mouse trap? Something caught in the fan?

Nick Badame Refrig/ACC · June 05, 2007, 08:13:10 PM

Hi Jim,

Sounds like the compressor relay is welded closed or your selector switch is broken. Not too uncommon.

Turn off the breaker, open up the inside cover and expose the electrical box, then grab your meter and

start testing the terminals on the selector switch, they need to be open in the off position, then see if you have relays

in your model. If so, test them also. You can also have some wires cooked together.

Let me know what you find
Nick-

Gary LaBombard · June 05, 2007, 08:15:40 PM

Hello Jim,
I would ask Nick Baddame for his advise on this issue, I believe it to be his field before asking anyone at Camping World which will tell you to replace them I am sure. We just put a new Coleman 13000 BTU AC rooftop on our S&S at Camping World and it cost about $1200 total installed for outside and inside AC units which you will have to buy both of.
Good luck, give Josephine our best also.
Gary

Gary LaBombard · June 05, 2007, 08:16:36 PM

Nick,
Looks like we were typing at the same time, well I was on track then and you are the man.
Gary

Nick Badame Refrig/ACC · June 05, 2007, 08:19:37 PM

Thank You Very Much Mr. LaBombard....

Nick-

Homegrowndiesel · June 05, 2007, 08:37:29 PM

Hello Jim
My First thought.
Bad switch. No electric to the fan, fused contact in the switch that sends electric to the compressor.

A proper operating switch would have broken the contact for the compressor, yet a fried fan motor can also draw more amps through the switch and cause it to melt, and work improperly.
Let us know what you find.

wireup the fan only. You already know the compressor isn't hurt. Check if the fan will run. I have used simple toggle switches for fan and compressor operation.

I like to bypass the safety low pressure cut out and run the compressor with low gas pressure, cut on the evaporator fan and blow 10 degree air. Looks like a fog machine. Of course you cannot run to long without freezing up the coil due to condensation. But cut off the compressor, keep the fan running, thaw the coil, and crank up the compressor. I like ICE COLD AIR.

Play with it for awhile.

Bill

Ps 5 new replies while I was typing, Man Am I slowwwww.

Nick Badame Refrig/ACC · June 05, 2007, 08:42:26 PM

I like to bypass the safety low pressure cut out and run the compressor with low gas pressure, cut on the evaporator fan and blow 10 degree air. Looks like a fog machine. Of course you cannot run to long without freezing up the coil due to condensation. But cut off the compressor, keep the fan running, thaw the coil, and crank up the compressor. I like ICE COLD AIR.

Bill, Thats one of the reasons I like you so much......You like to break the rules like me!
Nick-

jjrbus · June 06, 2007, 02:21:21 AM

Thanks for all the quick responses!!! Switch, relay? I'm am electricaly challenged!! here is link to parts list, does not seem to show board. www.dometicusa.com/pdf/3308733.009.pdf

fairlang · June 06, 2007, 10:59:13 AM

I had one of my units not start this year. Took cover off and found that the motor/fan shaft turned over much harder then it should have. I turned over the fan by hand many times and it freed up the shaft. Run great since. Jon

jjrbus · June 06, 2007, 11:44:18 AM

Took the outside cover off. No animals in fan! Fan spins freely by hand. No melted wires or any thing burnt. I would like to run power directly to fan motor. That would entail disconnecting capacitor. It has also been suggested to replace the start and run capacitors. I'm leery of capacitors it seems they are used to store electricity? I'm on a metal roof 12 ft in the air, I don't want to get knocked off!!! Do capacitors store electric, if so how do you discharge/disable one?

DrivingMissLazy · June 06, 2007, 11:54:34 AM

Quote from: jjrbus on June 06, 2007, 11:44:18 AM
Took the outside cover off. No animals in fan! Fan spins freely by hand. No melted wires or any thing burnt. I would like to run power directly to fan motor. That would entail disconnecting capacitor. It has also been suggested to replace the start and run capacitors. I'm leery of capacitors it seems they are used to store electricity? I'm on a metal roof 12 ft in the air, I don't want to get knocked off!!! Do capacitors store electric, if so how do you discharge/disable one?

With all power disconnected from the A/C, short across the capacitor terminals to discharge them.
Richard

Nick Badame Refrig/ACC · June 06, 2007, 03:02:47 PM

Hi Jim,

You have 3 relays on thet board that you pictured. The large black one is the compressor relay.

the other two white ones are for the fan and heat strip.

Nick-

NewbeeMC9 · June 06, 2007, 07:47:03 PM

If you have another roof air that is identical and works, swap capacitors and see if the problem follows it. then you know. I had to do that and buy a $5 capacitor to get AC going.

jjrbus · June 07, 2007, 06:57:57 AM

Thanks for all the responses, truly appreciated. I know very little electrically so am stumbling trough this as best I can. I do not know if there is a proper test for a relay. So with power off at breaker I checked the continuity of compressor relay and checked it against the second AC unit (thanks Newbe) With all power off the light on Continuity tester lights when places across the terminals of non functioning AC and does not light when touching terminals of second AC compressor relay.
This would indicate I have a bad relay. Unfortunately it is part of circut board which I have not priced yet. For a test It would be easy to switch board from good AC to bad AC. But the fan is not functioning on broken AC. I have not direct wired fan yet to see if it is working. Could there be something else wrong which might destroy good board?? The compressor comes on, why not the fan?