Dometic AC 13.5K fan failure.

[StanZZZ]

2005 Mobile Suites fifth wheel 36 ft with typical Dometic set up. Zone 1 Living area has 15K A/C with HP. Zone 2 is Bedroom with 13.5K Air conditioner only. Both are OE, Furnace is 42K all hooked together with a 5 button CCC thermostat.

Zone 1 works perfect. Furnace works almost perfect.

Zone 2 will run for ever on Fan only low or high

Zone 2 will run forever on Air conditioner on Fan low or on Automatic if difference between set temp and room temp is small enough to keep fan on low.

On Fan high or Auto with wide spread in temp the fan will start, the compressor will kick in and the unit will cool and run normally FOR NINE MINUTES. Then the fan will lock and the compressor will hummm. I don't know how long it will hummm as I always turn stat to zone 2 off before it pops a breaker.

Both capacitors check OK on my tester. I replaced my fan motor after I found some black windings and some burnt paper in it. That did not help and is a job I probably won't do again. I have two stats. One is a spare and it does it with either. I've checked all wiring and connections but it seems that if it was a bad connection it wouldn't start and run for nine minutes. I'm running only the one air conditioner and nothing else on my 30 amp home RV pad, but the problem started last winter in Florida on a robust 50 amp site.

I suspect the control board. I replaced it a couple years ago when the same air conditioner was running on it's own and not stopping until I pulled the circuit breaker. The board fixed the problem but there is one more small clue that puzzles me. When I installed the new board HEAT PUMP came up as a setting on the zone 2 tstat. It has no HP and never has and according to my Dometic manual no setting will be on the tstat that is not available.

Could they have given me the wrong board? Pretty sure I would have examined them pretty closely but I am 75 so you never know.

I have ruled out a compressor problem because it stays on when the fan shuts down. I have searched on all the on line forums I can find including 28 pages of posts by Doug. I not only can't find a solution I can't find anyone reporting the same problem.

I am open for suggestions.

[StanZZZ]

OK, I think this is my final post on this thread, intended for whoever comes later looking for info. I retriever my old motor from the trash and it is indeed a three speed motor. The board in the AC is designed for a three speed motor. The new motor is designed for a Penguin AC which I can only assume is a two speed motor so what PaulJ2 said is correct. I went to Dywer's web page and did a review on the product and explained the problem and solution. Don't know it they will post it. Thanks again to everyone who contributed.

[StanZZZ]

Most likely. But why did it work with the other motor. Was it a three speed. I dont have a medium speed on my tstat.

[PaulJ2]

For what ever was going on: Basically the motor was being fed voltage to two different speed windings at the same time and both were fighting each other.

[StanZZZ]

Doug, I have had this 5er 10 years and no one has been in that air conditioner until I changed the card about two years ago. Before 2008 maybe. So that yellow has been connected for 10 years, I think. It is possible that it was hanging there and I hooked it up to the new board but I don't think so. I'm usually more careful than that. I'm not sure what a spade is but my wire had what I call a female wire connector which slides on to the male wire connector marked yellow on the board. I am sure that the whole system worked that way for some period of time. I think that yellow wire was connected when the unit was built. I have two ccc tstats because I do. I really don't remember how I got the second one. As you may have gathered I've been a shade tree mechanic since 1959 and I help guys out at RV parks. I often end up with some extra parts.

I think Imgoin4it had the same situation I had only he had a whole new air conditioner while I had a new motor and board. I'm guessing that something in the stat makes that yellow wire cause a problem with late model motors and boards.

Anyway I'm happy I found you guys. I don't think it would ever have occurred to me to disconnect that wire without this web site.

[dougrainer]

imgoin4it wrote:
My acnd with heat pump had the yellow wire with the spade connecter but was not to be connected. During The techs conversation with dometic he was instructed to cut the wire off. He did and it was fixed.

You are not comparing the same system this post is about. The YELLOW wire is REQUIRED to run the reversing solenoid on a 5 button CCC Dometic system. Doug

[imgoin4it]

My acnd with heat pump had the yellow wire with the spade connecter but was not to be connected. During The techs conversation with dometic he was instructed to cut the wire off. He did and it was fixed.

[dougrainer]

StanZZZ wrote:
One more thing. The stat reset. I have two stats and I have done the reset several times to each unit.

You have 2(two) 5 button CCC tstats? WHY? Doug

PS, I misunderstood your Yellow wire. It is NOT to be connected to the Board. It is capped off. IF connected and NO Heat Pump, then it feeds back to the fan motor wiring and will cause your overheat/malfunction. THAT connection may have fouled up the HP reading from the board to the wall tstat. IF, after disconnecting and a reset does NOT remove the HP indicator, then the board has been failed. No Big deal, as you know it does not have a HP.
The Yellow wire from Dometic is CAPPED OFF. How did that wire get connected to the board since is did NOT have a Spade Terminal????

[StanZZZ]

One more thing. The stat reset. I have two stats and I have done the reset several times to each unit.

[StanZZZ]

Doug i would not disagree with someone with your experience. However, as soon as I disconnected that yellow wire the unit started working. As i said I even re connected it to make sure. I measured amps at the hook up. Not perfect but pretty close with nothing else running. Measured the temp of the fan motor. Right now I,m a happy camper. I ran the unit all afternoon. Thanks for your help and input. You sir are a great resource on this board.

[dougrainer]

StanZZZ wrote:
A couple more thoughts on this topic. When the unit was failing on high fan cool the fan motor was up to 160 degrees when it failed. Right after failure it was at 170. Thats the highest reading I took using my infrared thermometer.

I still have a setting for Heat Pump on my mode list in the CCC stat. I checked the dip switches and even turned the heat pump one on and off but its still there. I'm just going to ignore it.

HAVE you done the RESET on the Wall Tstat. THIS IS THE ONE TIME DOING A TSTAT RESET FIXES A PROBLEM!!!!!!!. The reset looks at the control boards and the DIP switches and only recognizes the switches that are ON and removes the other indicators. The yellow wire is NOT used on an AC. It is ONLY to run to the HP reversing solenoid. THAT is why it is capped OFF. Removing from the board does nothing. Dometic redesigned the CCC2 boards to do 2 things that the 5 button system could NOT do.
1. Get 3 fan speeds(that yellow wire)
2. IF the Reversing valve system fails, the CCC2 defaults to COLD air. The 5 button, when the reversing system failed defaulted to HOT air. There is logic in why they sometimes redesign systems. Doug

PS, you CANNOT use a multimeter to check for voltages and connections on the AC control boards. It will not yield results. You have to use a 60 watt light bulb assbly with 2 alligator clips.

[StanZZZ]

A couple more thoughts on this topic. When the unit was failing on high fan cool the fan motor was up to 160 degrees when it failed. Right after failure it was at 170. Thats the highest reading I took using my infrared thermometer.

I still have a setting for Heat Pump on my mode list in the CCC stat. I checked the dip switches and even turned the heat pump one on and off but its still there. I'm just going to ignore it.

[StanZZZ]

Thank you one and all. Imgoin4it wins the prize today. If you found this thread while trying to solve the same problem here is the solution. The yellow wire in the control board must be removed for the new motor to work with the current board. Doug, I did open up the other unit and as best I can tell the boards are the same. I did not pull the working unit board out to install in the other unit. I was about to and I thought about the yellow wire and the fact that it is for medium speed and I of course have no medium setting. I pulled on the yellow wire in the working unit and to my amazement it came loose and was capped on the end. At that point I had an awakening. I went to the problem unit and removed the yellow wire from the board, went down restored power turned the stat on hi cool and watched as the unit worked as designed. Wow, thank y'all for the help.

What I'm not sure about is the sequence of events. The first problem was a bad board which I replaced. I am almost sure the unit worked right after that. It was very hot last summer and I would remember if I had AC problems. So, I'm thinking that the new board worked with the old motor. When the unit started failing in high cool mode in florida I tried the caps and then removed the motor. The motor had black winding in places and burnt looking paper. My brother in law who is pretty knowledgeable about all things electric looked at a picture I sent him and pronounced it toast. So I installed a new motor. I think and it's nothing more than a thought, that the combination of the new board and the new motor, caused the failure I was experiencing. Removing the yellow wire from the board removes whatever the conflict is. After I had run the unit for an hour I shut it down and re attached the yellow wire. I then restarted on cool high and watched the temperature of the motor. It was climbing pretty fast so I pulled the yellow wire off the board and it was like I had shifted a gear. I could hear and feel the motor relax. Thanks again.

[dougrainer]

The control board has NOTHING----NOTHING to do with the AC model number. The control kits are separate from the AC. There are various boards and kits for the roof top AC units. So, you CANNOT give a Dometic AC model number and expect to get the correct control board. You use the OLD control board for the part Number. But, if BOTH roof AC's are identical, use the other AC control board to verify the correct Part Number. The Heat from either the compressor or the fan motor will NOT cause a problem on either one. You could have a defective fan capacitor that is not sending the correct voltage to the fan and it is running hot. But, you could just swap out the parts from the other AC unit to verify which parts are defective. Doug

[StanZZZ]

OK,Imgoin4it, I do not have a CCC2 board, nor do I have a Penguin. I have the duo therm original that came with the unit in 05. It is indeed a two speed motor but has a yellow wire for medium speed. But that was so for the past ten years and it worked fine. I do believe though that you are right about the heat of the motor. Today I will measure the temp when it shuts down.

Doug, I am sorry to say that I can't find the original board. I keep everything but I can't find it. But, as I shop for a board I can only find that one board for my model dometic. I deal with Dyers and they have always been very good about sending the correct parts. I also talked with dometic and I am aware of the need to either replace both units and the stat or to replace the board in the new unit. Sweet deal for dometic. Question, how hot is too hot on that motor or the compressor. Another question, would over heating cause the motor to seize while the compressor continues to run? That's what I think is happening. I will verify that today. Thank you one and all for responding.