Help-no 12 volt to bedroom A/C thermostat

[mrcomer]

We are opening up the camper and starting to clean and get ready for the season.
I was trying out the main A/C unit in the camper to see if it was working properly and after a couple of days of running realized it is not cooling as it should so I shut it off and decided to try the bedroom A/C and no power to the thermostat. I swapped the thermostats thinking maybe the bedroom one was bad but it lit up and operated the main A/c unit without a problem so it is not a bad Thermostat. I checked the fuses in the fuse panel and none of them showed as blown but I will pull the A/C fuse tonight and check with a meter to be sure. I pulled the cover off inside the bedroom and checked for 110volt and we have that. I found the end of the thermostat wire (phone style termination on both ends) and I hooked it to my network continuity meter and had continuity, no shorts. I even brought out a new phone cord and used it to connect the thermostat to the A/C unit but still not 12 volt. Is it possible I have a bad circuit board in the main A/C unit?

Thanks,
Mark

 

[wdk450]

Mark:
It sounds like you have the problem pretty well narrowed down. You DO know that the Duo Therm thermostats switch in a path to -12 VDC from the Heat and Cool wires to the air conditioner control box. You might want to verify if you can that +12 VDC is and -12VDC is getting to the AC control box thermostats and control power input connector P6. Looking at the component layout on the AC control board on page 12 of this manual https://manuals.heartlandowners.org...nits/Dometic/Brisk-Air-AC_installation_EN.pdf
I see that there is a 3 amp fuse F1 on the board in the area of the 12 volt control circuitry. 3 amps is probably involved with the 12 volt control stuff as that is not much amperage for any of the AC cooling stuff.

Kind of curious as to what changed during storage. You might want to hit all connectors concerned with some Cramolyn DeOxIt Electrical contact cleaner/restorer (Available on Amazon).

 

[mrcomer]

Thanks for the comments Bill, I'll try to look into that tonight.

 

[mrcomer]

Checked 3 amp fuse on circuit board and it is fine. I am getting 12 volts to the A/C before the board but not after. So now I am going to contact National RV Refrigeration In Shipshewana and see if I can get an appointment. I've talked with the owner in the past and feel confident he can fix me up.

Mark

 

[wdk450]

Checked 3 amp fuse on circuit board and it is fine. I am getting 12 volts to the A/C before the board but not after. So now I am going to contact National RV Refrigeration In Shipshewana and see if I can get an appointment. I've talked with the owner in the past and feel confident he can fix me up.

Mark

12 volts present before the AC control board, 12 volts not present after the control board. Sounds like the board or connectors.

Still funny whatever happened seems to be during storage.