Question about Dometic Rooftop RV Air Conditioner

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I have the same problem with my Dometic Duo Therm unit. However when i use a hot-stick on the fan wires coming from the new fan capacitor, there is no power. i can jump the fan to the hot side (WREN) on the capacitor and it will run on very low speed. I checked the control unit inside the air box and when the main cable is plugged in there is no power to the high or low sides of the card. when the cable is unplugged from the control module, i have power to both sides. WHAT UP?

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  • william simpson Aug 23, 2015

    Hi mike pierce, I want to help you with your question, but I need more information from you. Can you please add details in the comment box?



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  • 2 Answers


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Posted on Jan 02, 2017



  • 700 Answers

SOURCE: Duo Therm Quick Cool A/C fan motor cycles from low to high

sounds like the motor is either wired incoirrectly and getting 1/2 power all the time or it is going to ground. check out the woiring real good and duse your ohhm meter to check for gounds.

Posted on Dec 21, 2008



  • 1 Answer

SOURCE: I have a dometic duo-therm. No air coming through ducts.

I have a new Montana Mountaineer with a Dometic Duo Therm as well and experience something similar.

It appears that there are two options:
1. Open the vents in the unit and all the cold air will blow out of the AC as that would be the shortest path and the there is hardly any air coming out of the ducts.
2. Close the vents in the unit and it will force all the air through the ducts.

We let the air blow straight out of the unit during the day and then force it through the ducts at night to force it in the bedrooms. You could also open the vents in the unit part ways to get a combination.

I didn't figure it out immediatly either, but just look close at the unit and you can see that you can close the vents on the unit itself

Posted on Apr 20, 2009


  • 1 Answer

SOURCE: fan works on all speed, and low cool is working but does not change to medium or High

i need a wiring diagraham for a duo-therm mod# 54812-136

Posted on Jun 22, 2009


  • 1 Answer

SOURCE: duo therm air conditioner that the compressor will not start

your switch should be oopen but when it reaches 41 degrees it should open so the system shuts off before it damages the compresor by sludging it, i have the same unit and my compresor runs for 5 seconds and shuts off, i checked the amp draw at the compresor and it draws 21 22 amps trying to start after the initial 5 second run, but it wont come on againts a load so the comprresos equilizes and tries to start over again with out positive results. i bipass the external obverload on top of compresor terminals area, still no fix yet, the relay on the control board continious to send power to the compresor and still draws , so if there is a problem with the control relay i would open up and dont send power to the compresor so i dont think is the relay, i am a a/c service man for
35 years and do this for a living still today, by experience i think it is the compresor gone bad but will try by passing the relay just to see what happens, also it could be bad capacitor since it have a hard start relay and start capacitor (black )also a run (silver ) capacitor they check ok, there is no way to check the charge unles you install a saddle tap to check presures and rechage this unit i think the compresor replacement is the way to go ( around 250) plus labor and freon r22 e mail add

Posted on May 06, 2010


D. Floyd Kolb

  • 43501 Answers

SOURCE: Dometic Duo-Therm Model 57915.622 Fan will not start.

Hi, Sounds like your fan motor has gone bad...
Here is a tip about trouble shooting your air conditioner...

Air Conditioner Trouble -Review the Possibilities


Posted on Jul 19, 2010

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useually a sticking fan relay in the controll board this is the closeest unit to a home based cenral air system and i would leave this one to the experts if you want to trouble shoot there is a detailed wiring diagram on the back side of the pc board cover on the fan and compessor unit it self there is a seperate relay for each speed on your unit make sure getting power to selected relay if not trace wiring and do continutity tests back to themostat

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I'd have someone who's familiar with capacitors, (for safety sake), to test your fan run capacitor, and power to it. If capacitor is shot, fan won't start. Have to remove cover on upper unit, then cover on side at front where wiring is, to access it.

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