Dometic 4450037544 Air Conditioner PTCR Start Relay

The Dometic 4450037544 is an OEM replacement Positive Temperature Coefficient Resistor (PTCR) Start Relay designed for Dometic FreshJet 5 Series low-profile rooftop RV air conditioners. The PTCR, also commonly referred to as a PTCR start relay or thermistor, replaces the traditional compressor start relay and start capacitor found on select models, providing reliable compressor startup performance.

The PTCR works by supplying an initial burst of current to the compressor start winding during startup. Once the compressor is running, the PTCR's resistance increases rapidly, effectively removing the start winding from the circuit — all without any mechanical switching. A faulty PTCR can prevent the compressor from starting altogether, making this a critical component for proper air conditioner operation.

Key Features:

• OEM Dometic replacement part — ensures proper fit and function for FreshJet 5 Series units
• Positive Temperature Coefficient Resistor (PTCR) design replaces conventional compressor start relay and start capacitor
• Provides reliable hard-start assistance for the AC compressor
• Direct plug-in replacement for straightforward installation
• Also known as a thermistor or PTCR start relay

Troubleshooting Notes:

• To check continuity: turn the air conditioner circuit breaker OFF, disconnect the PTCR from the circuit, and test for continuity with a multimeter
• To check function: clamp an ammeter around the wire from the PTCR to the capacitor; when the compressor starts, a brief amperage reading of approximately one second or less should appear — no reading or a prolonged reading indicates a faulty PTCR
• Warning: Testing involves an energized circuit. Testing should be performed by a qualified service technician only

Use Dometic part number 4450037544 to confirm correct fitment for your FreshJet 5 Series air conditioning unit.