Yorkguard VI - Low Discharge Temperature (Heating)

Article ID: 188
Last updated: 19 Mar, 2024

York Heat Pump: Yorkguard VI

Re: Low Discharge Temperature (Heating)

The status lights on the module will indicate as follows: Red = On, Green = 6 Flash.

  • If, after energizing the compressor contactor for 1 hour, the Yorkguard module senses a compressor discharge temperature lower than 90 deg. the unit will enter a Low Discharge Temperature lockout which disables compressor operation.
  • This code is intended to indicate a compressor not running, but other issues that may result in a low discharge temperature reading may be the cause.

Qty Possible Causes:
Tripped Breaker
1 Bad Capacitor
Bad Compressor
1 Bad Contactor
1 Service Disconnect
Burnt Compressor Terminals
1 Bad Discharge Sensor
Extreme Low Outdoor Temperature


1. Check Outdoor Unit

  • Make sure the thermostat is set correctly and calling for Heat.
  • Remove the access panel of the outdoor unit.
  • Check for 230V inlet power on the compressor contactor.

2. Check Disconnect, Breaker & Compressor

  • Confirm the disconnect switch is inserted in the "ON" position.
  • Pull the service disconnect switch.
  • Check resistance between each leaving leg of the compressor contactor & ground.
    • Any resistance = Electrical Short Check Compressor Windings
    • No Short ⇒ Check Capacitor
  • Check the unit breaker at the breaker panel and reset if necessary.
  • (If no electrical short) Re-insert the service disconnect plug to restore power to the outdoor unit.
  • Re-check for 230V on the contactor inlet.

3. Check Contactor

  • Look for signs of burnt contacts (possible sticking contactor).
  • Contactor Pulled-In + No Compressor Operation:
    • Check for 230V across the leaving legs of the compressor contactor.
      • Inlet Power + No (or low) Outlet Power = Bad Contactor
      • Inlet Power + Outlet Power + No Compressor = Compressor off on Internal Overload or Burnt Compressor Terminals
        • Check compressor winding resistance
        • Visually inspect the compressor terminals 

4. Check Pressures & Temperatures

  • Turn off power to the outdoor unit by pulling the service disconnect or turning off the breaker.
  • Hook-up refrigerant gauges to the pressure ports on the unit.
    • Blue --> "True Suction" Low Pressure (Not the Suction Line)
    • Red --> High Pressure (either refrigerant line)
  • Hook an insulated thermistor to the compressor discharge line and monitor temperature.
  • Re-apply power to the outdoor unit.
  • Start the compressor with a call for heating from the thermostat.
  • Allow the system to operate for at least 10 minutes.
  • Observe refrigerant pressures + Discharge Temperature as the system operates.
Normal Pressure Range
Refrigerant 0-30 Deg O/D 30-50 Deg O/D
  • 70-100 Suction
  • 220-320 Discharge
  • 100-150 Suction
  • 250-375 Discharge
  • Normal discharge temperature = 130 to 160 deg.
    • Actual Discharge Temperature Below 100 deg. ⇒ Contact Supervisor

5. Check Discharge Sensor

  • Pull the service disconnect switch.
  • Power off the Yorkguard VI by disconnecting the   wire.
  • Remove the discharge sensor wires from the board.
  • Set the mulit-meter for 200K Ohms.
  • Check the resistance across the sensor (see York Sensor Resistance Chart).
  • Compare the sensor temperature to the actual compressor discharge temperature.
    • Sensor Temperature 10 deg. higher or lower than Actual Temperature = Bad Discharge Sensor
  • Re-power the board by re-connecting the   wire.

► If necessary, you can disable the discharge temperature sensor and the associated fault codes. (Confirm with Supervisor first.)

  • Power off the Yorkguard VI by disconnecting the   wire.
  • Disconnect the two discharge sensor wires from the Yorkguard board (tape-off the ends).
  • Re-power the board by re-connecting the   wire.
    • This will cause the Yorkguard to ignore the Discharge Temperature.

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Article ID: 188
Last updated: 19 Mar, 2024
Revision: 28
Access: Public
Views: 870
Comments: 0
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