tduncklee Posted April 4, 2022 Report Share Posted April 4, 2022 (edited) I have a 15K main Dometic Brisk II with the control board that connects to a single, 3 zone thermostat that controls all 3 ACs. I opened the unit up on top and found the evaporator completely plugged with sawdust (Thank you Dutchmen...).When cleaning the evaporator, I found the indoor temp sensor from the control board was not connect to anything. However, Dometic support says the lack of an indoor temp sensor would not cause the unit to be dead because the temp sensor is in the thermostat for the main unit.If I connect the thermostat to one of the grey thermostat wires that go to the front and back ACs, they work fine. The thermostat and main unit is dead when connecting to either of the black thermostat wires coming off the main control board.Talking with Dometic support they thought the control board was bad so I ordered a new one. That did not fix it. I have triple-checked that I do have 12VDC and 120VAC on the board.Any ideas on what else could cause this? UPDATE: For anyone else in this situation, you can not simply plug the thermostat into the black wires coming out of the control board. The RJ11 female - female connecter is required to flip the wiring. Also, you have to use a phone cord with identical wiring on each end. I picked up one at Walmart to test with and it did not work because the connectors were different on each end. When looking at the pin side with the wire towards you, the black has to be on the left. I cut one end off and put a new end on identical to the other end and using it with the coupler, my main AC came to life. Wiring everything back together I still had a problem. After putting a tone generator on the inside thermostat wire to determine which one it was up top, I put my new wire in its place. Everything worked! This meant the wire running from the main AC to the thermostat was bad. I gave the plug a good hard squeeze with the crimper and that fixed it. Apparently it was not crimped correctly at the factory. I hope this helps someone in the future. Edited April 4, 2022 by tduncklee Quote Link to comment Share on other sites More sharing options...
Kirk W Posted April 4, 2022 Report Share Posted April 4, 2022 While air conditioners are not my strongest subject, I think that if you visit this site you may find a service manual for the thermostat and air conditioner that you have. Quote Good travelin !...............KirkFull-time 11+ years...... Now seasonal travelers.Kirk & Pam's Great RV Adventure Link to comment Share on other sites More sharing options...
Wrknrvr Posted April 4, 2022 Report Share Posted April 4, 2022 Can you post a picture of your thermostat. By chance did Dometic have your reprogram you thermostat. Vern Quote Link to comment Share on other sites More sharing options...
tduncklee Posted April 4, 2022 Author Report Share Posted April 4, 2022 @Vern, No they didn't. However, I've got it figured out. I've updated my post with the solution. Thanks, Tim Quote Link to comment Share on other sites More sharing options...
Wrknrvr Posted April 5, 2022 Report Share Posted April 5, 2022 That’s very good detective work. To be able to notice the color sequence of wires is very good. Back in 07 when I went to a rv tech repair school, they did cover that wiring situation. Also re crimping that connection was a good idea. I would think about installing a new terminal end. Just to be safe. Or have one available to do ASAP. I carry a thermostat that I know works and a proper wire with me to plug into the control board on the Ac itself. Then I can eliminate all controlling items before the board. And test each Ac unit individually. Vern Quote Link to comment Share on other sites More sharing options...
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