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.
Where is your cat? A better mouse trap? Something caught in the fan?
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-
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
Nick,
Looks like we were typing at the same time, well I was on track then and you are the man.
Gary
Thank You Very Much Mr. LaBombard.... ;D
Nick-
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.
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-
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
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
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?
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
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-
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.
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?
Hi Jim,
Theese boards go bad, usually the contacts in the relays corrode or weaken which makes them
spark when energized. That spark ends up welding the contacts together. If you need a new board,
just give me the model # and serial # and I can ship it out.
Nick-
I cant &*%##& belive it. The fan on the second AC just stopped working!!!!!!!!!!!!!
This is in FL 90 degrees and 90% humidity.
Hi Jim,
Don't get too upset, A/C's are not worth getting aggravated over....
Start by, testing if you have current going to the motor, is the motor real Hot!
If not, backtrack to the source and elliminate things as you go. capacitor, relay, switch, burnt wires,......
Nick-
I cant &*%##& belive it. The fan on the second AC just stopped working!!!!!!!!!!!!!
This is in FL 90 degrees and 90% humidity.
Jim,
If it gets too hot for you & Josephine, use our house or the cabin until you get it fixed. Jack
PS: Since the second AC also failed, check the shoreline voltage. Low voltages increaqses the amperage.
I'm not upset, I seriousely contemplated useing a sledge hammer on AC's but it's too hot out.
Thanks to your help, I now have 1 running AC, the original one that quit. With nothing to lose I took the circut board from the 2nd AC, that is the one where the fan stopped running. I put the circut board in first one where the fan was not running but compressor would not shut off. Your internet diagnostic was right it was the compressor relay. It is running, blowing cold air, turns on and off everything there is fine.
Now to figure out 2nd one. I have no board for it at the moment. Befor ordering board, I would like to make sure that the fan motor is good. (its the fan that stopped running on this one) Running power to the fan motor has me a bit perplexed there are 6 wires running to the fan. Which ones would I have to apply power to?
1 green Ground
2 brown fan terminal of run cap
3 white C terminal of run cap
4 red circut board in AC unit fan low
5 yellow circut board in AC unit terminates hooks to nothing
6 black circut board in AC unit fan hi
It seems that if fan motor and board are bad it might be better to just replace whole unit. Just guessing but fan and board must be up near $200.
Thanks Jack and Paula, Josephine andI truly appreciate your generosity and friendship.
Also when I shorted across capacitor terminals I expected to see a spark. None was present?
Jim,
Sometimes the capacitor discharges it self. First, if you have a ohm meter you can test the capacitor.
If your meter has an audiable sound. the capacitor should sound briefly and then drop out. It's good!
If not, then the capicitor is bad.
To test the motor, send 115v to black "high" and white "nutral" while the capacitor is still in line.
Listen for a humm if the motor doesn't start, or will it start if you give it a spin by hand.
Let me know
Nick-
Thanks Nick, will play with it in the morning.
If you can swing it, I would just replace the broken A/C unit. You now have a bad board and a non-working motor.
If you shop around, you can get A/C units pretty close to $500 shipped with inside unit. You can possibly get just the top unit and not have to pay the $75 or so for the inside portion.
Jim.......While I was typing this post...Nick has answered capacitor testing post. Capacitor's life are limited to higher than design heat environment. Keep that in mind.....it may still test good "cooled" but fail in hot condition such as 120°F or higher.
You cannot run test a permanent split capacitor (PSC) fan (unless you spin it by hand) or compressor motor without an good starting capacitor....Period!
So if you want to replace capacitors, which is usually under $10 each and same time check for welded relays points via ohm meter with wires disconnected. If not infinity...welded points.
However...your problem maybe due to low voltage source which Jack had already mention. It should read at least 110v or higher the better...up to max spec (whatever label quote). Otherwise motor's will get extra hot to a point of burnout winding and cook out the fan's bushing or ball-bearing lube to run dry. And if it still working in low voltage...it will work harder with less cooling differential (between air intake & output)
I suggest to go ahead and replace inoperative A/C unit for new one and perhaps second unit...be ready for another one too.
Bottom line is to keep checking your power source for good voltage input....while in high load (ampere).
PS...I was rewinding electric motors for business in 1958 but choose to go MSU (East Lansing, Mi) instead.
FWIW
Sojourn for Christ, Jerry
I personally would not spend more than a couple of hours on this project, and no more than $200.00 since you can just buy a new unit for $5-600.00 and be done with it. Good Luck, TomC
There are reasons not to buy new AC. If I was on road, its not an issue just buy new!
But now I have the resources and the luxury of time. If I just buy new AC I do not learn anything. I enjoy helping people, it makes me feel good and now have the opportunity to let other people feel good by helping me. I enjoy the interacting with other people and maybe these posts will help someone else.
I recently inspected the same AC as mine (I did not think to pull the boards or caps, shame on me) That was replaced because it was not working well. The evaporator coil was 60% blocked with dirt. Was that the problem? well it was not helping any! I would have cleaned the coil to see if it was the problem. I would hate to spend $500 because of something simple!!
If it is the board and fan motor, it is not an issue just replace the whole unit. No sense in putting $200 in a $500 unit.
Not just low voltage issues in areas that have suffered hurricanes....Ours and four of our neighbors have had had transformer malfunctions this spring we came back from a car show and my bus had turned its shore power connection off because voltage had jumped to 143 volts . without protection this will burn out motors and anything running on a transformer...gg04
Thanks for all the help. I hotwired fan as per Nick, fan started right up, no delay, no hum nothing. Just started running! It seems problem is some where else.
Voltage here is averageing 121+ volts.
Need to get ahold of Nick to get a price on board. Its a Dometic 3104757.004 .
Should also replace capacitators while I'm up there!
Jim,
is the mo# of the whole A/C "57915"? this way I can look up the Capacitors
Call me... 609-263-2296
Nick-