QuestionThank you Larry for your quick response. I did some more searching on the internet and found this valuable website that has the service manual for my Duo-Therm AC/HP from Dometic (http://bryantrv.com/docs2/docs/acservice.pdf).
Thank god, I found that service manual. It was invaluable in troubleshooting my AC unit. I did find the problem which was the start capacitor on the second stage. The common terminal on the capacitor had come loose due to no solder on it. Also, for some reason the PTCR on one end was corroded and burnt (the end connected to the start cap.). Maybe it would be a good idea to purchase a new one. It did test out good though.
I soldered the common terminal on the start capacitor and cleaned up the PTCR with my Drimel tool w/ a round steel brush on the end. I then reinstalled the start cap. and PTCR. Waa-laa its working again. To answer your question about the thermostat I have a Duo-Therm Comfort Control Center, which is a four button digital. It operates both A/C units.
I would like to thank you for assistance. Maybe, you want to check out that website which has information for Duo-Therm roof mount A/C's and basement models like mine. Thanks JJ
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Followup To
Question -
I have a problem with my RV A/C Duo-Therm Model#
39424.602(basement style). It was working fine a
couple days ago and now it will only run on the primary side. The secondary side will not start even when I just use the fan setting. I noticed in the control box theres a starting capacitor for both the primary and secondary circuit boards and something called a PTCR that is connected to the starting cap. Could this be the problem? I pulled the unit out about 3 years ago to clean evaporator coils and everything looked great. The only thing was that the primary unit had a shraeder valve for adding more R-22 but the secondary unit did not. Is there a pressure switch on these units in case, you develop low operating pressure it'll shut down the secondary stage totally(no fan-nothing)? Is there a way a person could add a shraeder valve to the secondary stage? Oh, BTW these units are identical 13,500BTU's sitting side by side incased in sheet metal.
Answer -
Hi James,
I have been looking for a wiring diagram for your particular unit, but have not been successful.
It seems odd that the indoor fan will not turn on. It sounds as if there is no 110 volt power to unit, or either the transformer is not powering the controls. Please check on the incoming power, then test the transformer for an output voltage of 24 volts.
Do you have separate thermostats for the two units, or is there just one thermostat with two different stages of cooling? There are so many variations of HVAC systems and wiring amoung various RV's. If you have a fax machine available, perhaps you could send a copy of wiring diagram, that way we could go over it together.
The unit which has the schrader valve installed, evidently was installed by someone who needed to either test or add refrigerant. The other unit, may not have needed refrigerant. As regards to the pressure switch, some of the higher end units do have them, others do not. Again without wiring diagram, its hard for me to answer question properly. The PTCR relay, from your description of its location, may be a compressor start relay, which uses a smaller capicator for hard starting situations, along with its normal run capacitor.
James, it sounds like you have a very nice hvac system installed in your coach, and that you do maintained it very well. Its so refreshing to hear reports like this one.
If I can further assist you with this, please do not hesitate to contact me.
Regards, Larry
AnswerHi JJ:
Thanks for the reply. Its always good to hear about the repairs done by owners. This is why we are here to assist anyway that we can. Thanks too for the address of manuals. I will check it out and keep it for future references too. Im happy you found the source of problem with your A/c unit.
The relay that, you refered to, which has a burnt terminal on it, definitely should be replaced. Most likely the contacts inside, are pitted, and the resistance is causing heat to flow up to the terminals. It could cause your compressor to fail, should it malfunction. The cost of the relay is inexpensive compared to a compressor replacement.
JJ, If I can be of further assistance, please do not hesitate to contact me.
Regards, Larry
