Intermittent Heat and AC problems

Recently, a friend asked me to take a look at the Dometic analog thermostat in his 2004 Sunline Travel Trailer. He was having intermittent heat furnace cycling problems and had found he could make his furnace turn on by wiggling the control wires inside the thermostat. I suspected a broken or loose wire but, instead, found the pins on control wire terminal block were not properly soldered to the thermostat printed circuit board. Two minutes with a soldering iron and his heat cycled properly.

Since the same model thermostat is used by Heartland, I decided to take at look at the one in my 2008 Sundance 2900MK. Not only was I able to cycle the AC and heat by pushing on the terminal block, I was able to pull the block completely off the board. Talk about cold solder joints.

I replaced the thermostat with a Hunter digital as described elsewhere on this forum. The Dometic analog is on my work bench awaiting repair.

Executive summary…. If you have a Dometic analog thermostat and are experiencing intermittent cycling problems with either your furnace and/or AC, check for a poorly soldered control wire attachment block inside the thermostat.

- Jack
 
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