RV Repair: Air conditioner, air conditioner, compressors

Question
Hello Bill,
I have a Coleman Mach 15 and the compressor seems to run continuously. The unit cools great, but when the selected temperature is reached and the fan turns off, the compressor keeps humming along. Actually , the compressors runs whenever power is supplied to the unit. Any ideas?
Thanks

Answer
Patrick, It sounds to me like the control board in the upper assembly has gone bad. Coleman have a board in the compartment where the air goes into the unit. Pull the grill of from the inside and you should see where 4 wires are connected to a metal box. Mark the wires so you can put them back in the correct places and then pull all the wires off. If it continues to run then the metal unit you pulled the wires from needs to be replaced. If when you unplug these wires it stops then I would say it is in the T-Stat. That is as long as none of them are shorted together somewhere in the walls. The way they work is that when the T-Stat sends power to the unit it activates a relay and turns on the air. If you need to replace the metal box be sure to turn off the power first and they are pretty easy to replace. Just disconnect the molded plug to the upper unit and the wires from the T-Stat and then you can pull the cover off and remove the 110 wires and reverse the operation to put the new one in. I hope that this helps you and if you need more help feel free to ask and I will do my best. Bill