Steve from SoCal Posted July 27, 2018 Report Share Posted July 27, 2018 I posted a thread in fifth wheels about my AC, fans run no power to the compressors, main unit stopped working, next day the bedroom unit died. Fans run on the roof units, reset the t-stat and, checked for power on t-stat board it checks OK. Steve 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
TXiceman Posted July 28, 2018 Report Share Posted July 28, 2018 WHat brand units do you have? Ken Amateur radio operator, 2023 Cougar 22MLS, 2022 F150 Lariat 4x4 Off Road, Sport trim <br />Travel with 1 miniature schnauzer, 1 standard schnauzer and one African Gray parrot Link to comment Share on other sites More sharing options...
Steve from SoCal Posted July 28, 2018 Author Report Share Posted July 28, 2018 Dometic, with Duo-Therm 4 button T-stat. Steve 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
NeverEasy Posted July 28, 2018 Report Share Posted July 28, 2018 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 Chet & Deb '01 Volvo 660 w/ Smart '19 Forest River Columbus 320RS 5th wheel 2022 Chev 2500HD Long Bed Retired CWO4, USN and federal service Electronics Tech/Network Engineer/Welder/Machinist Link to comment Share on other sites More sharing options...
Wrknrvr Posted July 28, 2018 Report Share Posted July 28, 2018 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 Link to comment Share on other sites More sharing options...
Steve from SoCal Posted July 28, 2018 Author Report Share Posted July 28, 2018 Cooling again, Turned out to be a low voltage condition on the DC bus. Steve 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
DQDanny Posted July 29, 2018 Report Share Posted July 29, 2018 Glad you are cooling off......is that with both A/C's? And curious, can you explain what caused the low DC voltage? Link to comment Share on other sites More sharing options...
Steve from SoCal Posted July 29, 2018 Author Report Share Posted July 29, 2018 Quote 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. Steve 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
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