YHE/YHG - Code 3 - High Pressure - Cooling

Article ID: 597
Last updated: 6 Apr, 2023

York YHE / YHG Heat Pump: Cooling

Re: High Pressure Fault - Last Mode Heat Pump

The heat pump was running in cooling mode and the high pressure switch tripped.

High Pressure Lockout is indicated by a 3-Flash LED pattern on the outdoor unit control board.

X/L Output

Qty Possible Causes:
Refrigerant OverCharge
  Bad I/D Expansion Valve
Bad Condenser Motor / Capacitor
Low Outdoor Airflow
Refrigerant Restriction
2 Bad Pressure Switch


1. Check Condenser Motor

  • Set the thermostat to call for COOL.
  • At the outdoor unit, confirm that the outdoor fan starts and operates properly with the compressor.
    • Fan Operates Normally → Step 2. Check Refrigerant Pressures
    • Compressor + No Fan ⇒ Check for a field-installed low ambient kit.
      • No Low Ambient + No Fan = Bad Condenser Motor or Capacitor

2. Check Refrigerant Pressures

  • If the heat pump is in lockout, reset by removing 24VAC power to the outdoor control board.
  • Initiate a call for COOL from the thermostat.
  • Hook-up refrigerant gauges to the pressure ports on the unit.
    • Blue ⇔ "True Suction" Low Pressure
    • Red ⇔ High Pressure (small liquid line)
  • Place an insulated temperature probe on the liquid line near the outdoor unit.
  • Allow the unit to run for at least 10 minutes.
  • Monitor pressures and temperature as the system operates.
    • If pressure exceeds Normal Range and kicks-off on Hi Pressure safety in the first 5 minutes = Bad Overcharge or No Outdoor Airflow
    • If the compressor never kicks on & the control locks-out on Hi Pressure ⇒ Suspect a Bad Pressure Switch

4. Check Sub-Cooling

  • Record "Saturation Temperature" from the discharge pressure gauge.
  • Subtract the Actual liquid line temperature reading.
    • Saturation Temp - Liquid Line Temp = Sub-Cooling
      • Sub-Cooling > 13 deg. + High Discharge Pressure + Normal or High Suction Pressure = Overcharged
      • Sub-Cooling > 13 deg. + High Discharge Pressure + Low Suction Pressure = Bad I/D Expansion Valve or Refrigerant Restriction
      • Sub-Cooling < 2 deg. + High Discharge Pressure + Hot Liquid Line = Low Outdoor Heat Transfer Clean Condenser Coil and recheck pressures.

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Article ID: 597
Last updated: 6 Apr, 2023
Revision: 7
Access: Public
Views: 119
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