YorkGuard VI - Low Discharge Temperature (Cooling)

Article ID: 189
Last updated: 15 Jan, 2018

York Heat Pump: Yorkguard VI

Re: Low Discharge Temperature (Cooling)

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 operating, but other issues that may result in a low compressor discharge reading are often the cause. 

Qty Possible Causes:
Tripped Breaker
Bad Capacitor
Bad Compressor
Bad Contactor
Burnt Compressor Terminals
Bad Discharge Sensor
1 Bad Indoor Expansion Valve


1. Check Outdoor Unit

  • Make sure the thermostat is set correctly and calling for Cool.
  • Remove the access panel of the outdoor unit.
  • Check for 230V inlet power on the compressor contactor.
    • No Power →  Step 2. Check Breaker & Compressor
    • Power Present --> Check Diagnostic Light on Board
      • Diagnostic Present --> Reset by removing "R" and "Y" from the board.

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.

3. Check Contactor

  • Contactor pulled-in but 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

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
    • Red --> High Pressure (liquid line)
  • Re-apply power to the outdoor unit.
  • Start the compressor with a call for cooling from the thermostat.
  • Allow the system to operate for at least 5 - 10 minutes.
  • Observe refrigerant pressures.
    • Normal R-22 Pressures = 55 to 80 psig Suction, 150 to 270 psig Head.
    • Normal R410A Pressures = 100 to 150 psig Suction, 200 to 400 psig Head.
  • Hook an insulated thermistor to the compressor discharge line and check temperature.
    • Normal discharge temperature = 130 to 160 deg.
      • Discharge Temperature Below 100 deg. --> Contact Supervisor

5. Check Discharge Sensor

  • Pull the service disconnect switch.
  • 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.
    • Replace sensor if necessary.

► 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 "R" wire.
  • Disconnect the two discharge sensor wires from the Yorkguard board (tape-off the ends).
  • Re-power the board by re-connecting the "R" wire.
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Article ID: 189
Last updated: 15 Jan, 2018
Revision: 8
Access: Public
Views: 1571
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