Front Duo-Therm A/C not working

[vacationer04]

My front Duo-Therm A/C will not operate in any function. I went on a 5 hour trip last Saturday with the GEN running for A/Cs and fridge. Both worked fine. For 5 days on 50A shore and stats programmed all went fine but yesterday after turning them off, unplugging the cord and starting the GEN I turned them back on after the GEN voltage came up but only the rear would come on. The front will not power up even on the manual fan only setting. The breakers in the distribution were not tripped. Where do I begin to check to determine the problem? Can it be the stat? I am confirmed to attend the RALLY so I need to get this figured out. I can't get into any local RV shop for more than 30 days which won't help much now. If I can diagnose it but can't get parts before I leave for Elkhart maybe I can get them there.

[adamfolger]

If you have the 5 button tstat, push the switch to off and press the mode and zone buttons simultaneously and slide the switch to on. The display will show FF. If FF displays release the mode and zone buttons. The display will then show normal and the reset is complete. If EE displays during procedure, repeat the above. EE shows that there is a communication cable problem. Remove the t stat cover and plug / unplug the com (phone) cable several times and spray with electrical contact cleaner spray. It has been noted that florescent lights can interfere with the working of the t stat. Shut off all florescent lighting. My t stat was acting up and after I stopped using the florescent light over the kit sink, all was well. Hope this helps......ps, you did check the 12 v fuse to the t stat, right?

[guardrail53]

Just a thought, but did you check the breakers on your generator? One may have tripped and not letting the power get to your A/C? I say this because you said everything was working fine on shore power, and the problem started after you switched to the genny! Hope it is something simple like this! Rail!

[vacationer04]

I have one-by-one reset every breaker in the distribution panel, all fuse panels and the GEN. I have removed and reset the t-stat. I have gotten inside of the lower part of the A/C above the filter and found that I do have 117V AC power coming into the box. If I turn the A/C on either fan or A/C I get one faint click but no other functions or sounds like the compressor is engaging. Is there a way to check the board with a voltmeter? The 3V fuse there was not bad- checked it with the meter. I still have the box exposed for access. Is there a replaceable relay there?
I removed the shroud up top and the fan spins freely by hand. Which wires have the incoming power up top? There is a small compartment that contains three parts that are capacitors, hard start or similar items. [ATTACH]137396[/
[ATTACH]137397] Which one do I start with to eliminate a defective part?

[CadillLinc]

As a way of narrowing the problem, try swapping capacitors, etc. between the front and rear units. I recently did this on my 2 AC's and determined that one of the control boxes was bad. Replaced it and all is well.

Gene M
2004 Monaco Knight

[vacationer04]

Thanks for that advice. I had told my wife this morning that if I didn't get more specific advice that was going to be my next step. I probably will start with the upper items like capacitors before changing the lower power boxes unless your issue was there. Which part did you eventually find your trouble to be in?

[CadillLinc]

I have a different brand AC than yours. Mine are Dometic Penguins. But the principle is the same. Mine has a 6" x 6" x 1.5" metal control box with a circuit board in it, mounted just above the ceiling grille. I checked the circuit board and could see no problems. It didn't have any capacitors, but did have what I think are a couple of small relays soldered to the circuit board. But, I had no way to test the control box/circuit board other than to swap with a good one. Amazon sells new Dometic control boxes.

Gene M
2004 Monaco Knight

[vacationer04]

I, too, have Dometic Penguins, 13500 btu, (model# 600315.321) and our coaches are of the same year so both should be identical. I did just swap power boxes with no improvement. My next move will be to test or swap capacitors and such up top. I am getting 117V at the front A/C incoming Romex power source. But the rear board made no difference up front so I returned it and the rear does still work so it has to be up top somewhere. Because of the difficulty of disconnecting and reattaching the AC power wires twice up front, I did not try to connect the front board at the rear.

[vacationer04]

Even after swapping all of the capacitors and related items in the upper electrical section of both A/Cs I still have no action from the front unit but the rear works on either set of components. The fan is free spinning by hand but neither it nor the compressor respond to power through the normal procedures. I have run my GEN during the tests to be sure of getting full voltage to it. I am not sure which wires up top are for the fan or comp to test them offline. I would not hesitate to replace the whole unit if I can verify that it is defective. HELP!

[jacwjames]

You may have to try and replace the communication cable, it looks like a phone cable but is wired different. This is a fairly common problem so if you do some searches you will get some hits. I believe it runs from the rear AC to the front

Once you get a cable you can run it and see if that fixes and then figure out how to run it, some people just put through the vent duct.

[vacationer04]

I am getting more desperate to get this working for the trip to the Rally. Can anybody tell me how I can by-pass the board and run the A/C manually while I am in motion? We can get by with only rear air after we arrive but need the front while we are on the road. If I could use it normally it would be running full on so that shouldn't be any different. I can't believe that the fan and compressor both died at the same time but how can I power it up to find out? I am doubting the communication cable only because it comes to the front and then goes rearward from there from my observation of the front wiring there.

[Gearhead383]

I understand we're grasping at straws at this point, so I'll throw in my .02. Have you tried to plug back into shore power and see what happens? Even if it's just a 110v power, it would still be enough to run the fan on your front AC. Perhaps the problem may be else ware. It sounds like you swapped most everything from the rear unit so I'm thinking maybe wiring or power source. Like I said, just grasping here. Good Luck!

[CadillLinc]

The Dometic Penguin Installation Manual can be found here: http://www2.dometic.com/1f24ead8-631...87ce6bad.fodoc
In the back are wiring diagrams. After reviewing them, maybe you can figure out how to hot wire your unit.

Gene M
2004 Knight

[bruceisla]

Go here ... everything you need ....

R.V. Air Conditioner Troubleshooting