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A/C no bueno

Steve from SoCal

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Searched the internet for a schematic.  There are control relays (depending on model, one or two) and start and run capacitors to be concerned about.  Start capacitors do go bad over time.  They are readily available.  Might want to start there. The schematics are at the bottom of this pdf. 

https://cdn.ltvdns.com/leisurevans.com/owners/3rdparty/Dometic-RoofTop-AC-installation-operating-manual-651916 .pdf


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  Did you smell any burnt wire smell.


 There is a little device on the start cap that can burnout and will cause no power to the compressor. I have never found that part separate . It is called a pctr. Yes that is what it is called. It can be obtainled with a start capacitor kit for your ac.

 Now if that is not the problem it is either the thermostat or the board itself.


i am on vacation,.   I think,.   Vern

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I tested the voltage at the tstat, I was seeing 8.5 volts, the DC is supplied by a battery bank and charger/converter.     I replaced the charger/converter about a year ago, the battery "bank" consists of a single truck battery right now.     I have a hunch the battery is shorted, I jumpered another truck battery into the system and have no issues.    

The battery monitor showed 12.9 volts with no load and,  yes both roof top units work correctly.    I thought the low voltage was initially a bad phone cable between the tstat and the control module, I pulled the cables and buzzed them out.    I had a strong hunch the problem was a control issue, both units failing within a day with the same symptoms was too coincidental.   

The only things that are DC in the trailer are lights, HVAC control and, dump pump.     The pump sounded a bit weak the last time I ran it, I was thinking it may need brushes?     Now I realize the battery was slowly loosing voltage.     The lights are 8-12 volt so they didn't seem to telegraph the situation.   


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