Question about Dometic Rooftop RV Air Conditioner

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We did as requested and used a stop watch and pencil to record our Dometic unit's cycle. We found that the compressor will only run 9-10 minutes and then shuts off, only to restart in 2-3 minutes regardess of inside temp. We timed this over a14 hour period and the only time it shut off properly was late at night when it had finally reached the temperature set on the comfort control center. During the heat of the day, the fan ran for 53 seconds after the compressor shut off, then all would shut down only to restart within 2-3 minutes. This was consistent for hours without our intervention whatsoever. Finally, the compressor and fan started shutting down at the same time late that night. next morning, it took the temp to rise in the rig to a total of almost 5 degrees above the set temp for it to cut on and then it began it's cycle of 9-10 minutes compressor time and then starting up again 3 minutes later. I assume that this afternoon, when it gets hot again, the compressor will still be cutting off every 10 minutes but the fan will start going into high gear for the 53 seconds. What's the deal? Shouldn't the unit stay on until it reaches the set temp? I am not asking it to go 20 degrees below the outside temp. I am setting it to 73 degrees with it being only 83 degrees outside. Yet, because it keeps cutting on/off, it is taking it forever to get to the set temp! Not to mention the fan kicking into high gear during the hottest part of the day. We have extended warranty and want to get this fixed but the last serviceman didn't see it acting up and didn't want to replace anything until he knew for sure. We know it is not the amperage and the sensor that clips into the coils was not the problem. We visually know that the coils are not freezing up. Please help!

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Hello kamper2 - Sorry for the delay in answering. I had a response prepaired but something cleared it on me about 2AM last night and I just couldn't think any more. Sounds like your problem is similar but different. I don't think you have to spend any more time on the roof looking at the roof unit. I have been working with a tech and Dometic for over 6 weeks. Right now I am running my A/C on an extension cord out my window and over the the power pedestal for power. The 12 VDC to the A/C circuit board is coming from a car battery sitting on my kitchen floor. The communication cable is a 25' telephone extension cord draped over my kitchen slide over to the CCC. Last week end I turned off all power to the trailer (110VAC and 12VDC) and sat here all day running just the A/C. It shut down 6 times. This was an effort by Dometic to eliminate RF energy affecting the microprocesser on the A/C control circuit board. Apparently the CCC and A/C control circuit board have some idiosyncrasies that aren't well explained. I also have an extended warranty on my A/C with Dometic. I'm thinking they believe RF energy may be picked up via the communication cable and affecting the microprocessor. Do you have a cell phone, wireless router for your computer or telephone or something that may put out noticeable RF energy? If you do, turn it off for a while to see if that may be related to the shut down's. I'm still working on my problem and no solution or reason yet. The circuit board in my A/C has already been replaced. I am assuming you do not have an icing problem with the problem A/C. If for some reason you decide to replace the communication cable from the CCC to the A/C circuit board, be aware that a typical telephone extension cord will not work. You must replace one of the plugs so the wires are straight through (pin for pin) and not reversed as the typical telephone extension cord is. Good luck with your detective work! azbill375

Posted on Aug 13, 2008

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