Bryan fast-cycled the training unit for a demonstration of the shift between cooling and heating mode on a heat pump. When he put the unit back into cooling mode after the demonstration, the COR thermostat kept rising despite the low outdoor temperature. So, he disconnected the circuits one by one, and the thermostat stayed high until Bryan disconnected the orange wire.

He then bugged red to orange and on the outside and checked the amperage on the O circuit (which was low), and the temperature dropped again. You will get a little amperage spike on the orange wire when energizing the reversing valve solenoid, as the solenoid is an inductive load. Bryan hypothesized that the O circuit must have gotten damaged when he fast-cycled the unit for training purposes.

The new COR thermostat that we installed was reading the normal temperature, though the humidity sensor hadn’t yet acclimated. So, Bryan determined that rapid cycling did indeed cause a damaged O circuit.