Dometic™ Duo-Therm 3310731.009 RV Air Conditioner PTCR Start Relay

The positive temperature coefficient resistor, or PTCR has replaced the compressor start relay and the start capacitor, on some models.

It should be checked in two different ways: First, check continuity. Turn the air conditioner circuit breaker to OFF. Disconnect the PTCR from the circuit. Check for continuity. The second check to take is an amperage reading. Clamp an ammeter around the wire from the PTCR to the capacitor. Turn the air conditioner circuit breaker to ON and start the air conditioner. When the compressor starts, there will be an amperage reading for approximately one second or less. If there is no reading, or if there is a prolonged reading, the PTCR is faulty. NOTE: THIS IS AN ENERGIZED CIRCUIT. SHOCK CAN OCCUR IF NOT TESTED PROPERLY. TESTING TO BE DONE BY A QUALIFIED SERVICE TECHNICIAN.