Originally Posted by daveb
BTW If I drive with the thermostat set to cool and I turn on my inverter, the starcool thinks it's on shore power and will try to cycle. My inverter can't handle the load and will trip off. Probably has nothing to do with your problem though.
If this is happening then you have a wiring error or bad relay. One of the relays on the Startcool relay panel is there is to isolate the "110" system while the van is running. The 12 volt input on the input of the cool line of the thermostat comes from this relay. This is wired on the always on connection of the relay, so it could be bad or it is not receiving a 12 volt ignition on input.
The below diagram shows the light blue ignition input, which if picked should take 12 volts away from the thermostat.
For the original poster, you can measure the input to the thermostat(RC) at terminal 4 and the output (Y) at terminal 3.