York Heat Pump: THGD
Re: Contactor Won't Energize
The contactor on the outdoor unit doesn't pull-in.
- No Compressor Operation
- No Outdoor Fan Operation
Qty |
Possible Causes: |
2 |
Bad Hi Pressure Switch |
|
Bad Low Pressure Switch |
1 |
Wrong Defrost Pin Selection (Replacement Board) |
|
Condensate Overflow Switch Open |
|
No Call for Y |
|
No 24V |
|
Loss of Charge |
|
Bad Defrost Board |
|
Bad Contactor |
CHECKOUT:
1. Check Line Voltage Power
- Disconnect power to the outdoor unit by pulling the service disconnect.
- Remove the outdoor unit electrical access panel.
- Look for any signs of burnt wires or controls.
2. Check Low Voltage Power
- Check for 24Vac between Common (Black) and R (Red).
- No Voltage = No Power to Air Handler, Blown Low Voltage Fuse or Bad Wiring
- Check for 24Vac between Common (Black) and Y (Yellow).
- No Voltage = No Call from Thermostat, Condensate Overflow Switch Open or Bad Wiring
- Check for 24Vac across the Contactor Coil.
- Power + Not Pulled-In = Bad Contactor
- No Power ⇒ Jump the Test Pins on the Defrost Board and Recheck for 24VAC
3. Check Pressure Switch Circuit
- Check for 24Vac from Common (Black) to each Pressure Switch terminal on the defrost board.
4. Check Pressure Switches
- There are two pressure switches wired in series to the Defrost Board:
- High Pressure Switch = Yellow Wires
- Low Pressure/Loss-of-Charge Switch = Black Wires
- Find and cut the factory splice which connects the (Yellow) High Pressure Switch to the (Black) Low Pressure Switch.
- Check continuity across both pressure switches.
- High Pressure Switch Open = Bad High Pressure Switch
- Low Pressure Switch Open ⇒ Check Refrigerant Pressure
- Sufficient Pressure = Bad Low Pressure Switch
- Low or No Pressure = Loss of Charge
5. Check Defrost Pin Selection
- If the defrost board has recently been changed, make sure that the defrost pin is in a numbered position.
- A replacement defrost board will not energize the compressor contactor in the default "P" position.
- See Replacement Defrost Board article for details.