Heat Pump - Compressor not Operating

Article ID: 187
Last updated: 30 Jan, 2017

Heat Pump: YorkGuard VI

Re: Compressor not Operating

These heat pumps are equipped with a YorkGuard VI module which monitors and controls unit operation and defrost.

An X/L terminal on the YorkGuard module sends a signal inside to flash a diagnostic light at the thermostat.

► Unlike previous models, the YorkGuard VI does not flash the actual diagnostic code at the thermostat, only a code 2, 3 or 4 to indicate a "Soft" or "Hard" lockout.

Possible Causes (From Most to Least Likely): Qty
Unit in Lockout
No Power to O/D Unit
Bad Capacitor
Thermostat Set Incorrectly
Bad YorkGuard Module


1. Check Outdoor Unit

2. Check Breaker & Compressor

  • Pull the service disconnect switch.
  • Check resistance between each leaving leg of the compressor contactor & ground.
    • Any resistance = Electrical Short --> Check Compressor
    • No Short --> Check Capacitor
  • Check the unit breaker at the breaker panel and reset if necessary.
  • Re-insert the service disconnect plug to restore power to the outdoor unit.
  • Re-check for 230V on the contactor inlet.
    • No Power --> Loose or Burnt Wires in Disconnect or Bad Breaker

3. Check Current Diagnostic Codes

  • Observe the two LED lights on the control board.
  • See YorkGuard VI Status and Fault Codes

4. Check Previous Diagnostic Codes

  • Turn the thermostat to the "Off" position.
  • Press and release the "Last Error" button near the top of the YorkGuard board.
    • The board will display the last 5 diagnostic codes, starting with the most recent.
    • See YorkGuard VI Status and Fault Codes
      • When finished reviewing previous codes, be sure to clear the fault history before proceeding.
        • Press and hold the "Last Error" button until both LEDs flash two times.

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Article ID: 187
Last updated: 30 Jan, 2017
Revision: 12
Access: Public
Views: 110
Comments: 0
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