Yorkguard VI - High Pressure Lockout - Heating

Article ID: 237
Last updated: 23 Oct, 2020

York Heat Pump: Heating

Re: High Pressure Fault - Last Mode Heat Pump

The heat pump was running in normal heat mode (not in defrost) and the high pressure switch tripped.

A High Pressure Lockout is indicated by the following LED pattern on the outdoor unit control board:

  • Green = Off
  • Red = 2 Flashes

X/L Output

  • 2 Flashes at Thermostat = Soft Lockout
    • Switch opened two times in 6 hours.
    • Reset by cycling thermostat or jumping Test pins.
  • 3 Flashes at Thermostat = Hard Lockout
    • Four Soft Lockouts in 12 hours.
    • Reset by cycling 24VAC power to the board.

Qty Possible Causes:
1 Refrigerant OverCharge
1 Bad Expansion Valve
1 Bad Blower Motor / Capacitor
Bad CFM Board
Low Indoor Airflow
Refrigerant Restriction
Bad Pressure Switch


1. Check Indoor Airflow

2. Check Blower Motor

  • The YZE & YZH heat pumps should be matched with a Variable Speed Indoor Blower.
  • At the air handler, confirm that 240VAC is being supplied to the motor.
  • Confirm that 24VAC is present between "C" and "G", "Y1" or "Y2".
    • No 24VAC power = No signal from thermostat
    • 240V Power Present + 24V Power Present + No Blower Operation = Bad Blower Motor or Bad CFM Board

3. Check Refrigerant Pressures

  • If the heat pump is in lockout (still flashng a code), reset by removing 24VAC power to the outdoor control board (remove "R" or cycle power to the air handler).
  • Initiate a call for heat from the thermostat.
  • Hook-up refrigerant gauges to the pressure ports on the unit.
    • Blue --> "True Suction" Low Pressure
    • Red --> High Pressure (either refrigerant line)
  • Place an insulated temperature probe on the liquid line between the evaporator coil & O/D expansion valve.
  • Allow the unit to run for at least 10 minutes.
  • Monitor pressures and temperature as the system operates.
    • If pressure exceeds Normal Range or kicks-off on Hi Pressure safety in the first 5 minutes = Bad Overcharge or No Indoor Blower Step 6. Check Air Filter & Indoor Coil
    • 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 + High Suction = Overcharged
      • Sub-Cooling > 13 deg. + High Discharge + Low Suction = Bad Expansion Valve
      • Sub-Cooling < 2 deg. + High Discharge = Low Indoor Heat Transfer Step 5. Check Heat Pump Temperature Rise

5. Check Heat Pump Temperature Rise

  • Check to make sure the indoor fan is operating.
  • Disconnect auxiliary heat (remove "W" at the air handler or thermostat).
  • Check the Return Air Temperature at the air handler (at the filter if possible).
    • High Return Air Temperature (more than 85 deg.) = Heat Recycling
  • Check the Supply Air Temperature near the air handler (in a straight duct run if possible).
  • Calculate the Temperature Rise = Supply Air Temperature - Return Air Temperature

6. Check Air Filter & Indoor Coil

  • Remove Air Filter and Check for a Dirty Indoor Coil
    • If Indoor Coil is OK ⇒ Re-Check Temperature Rise with the filter removed.
      • No Change = Restricted Ductwork or Low Blower Speed Step 7. Check Duct Static Pressure
      • Temperature Rise Becomes Normal = Clogged Air Filter ⇒ Replace Filter & Re-check Pressures

7. Check Duct Static Pressure

  • Check the return static pressure (between the air handler and filter if possible).
  • Check the supply static pressure.
    • High Static = Above 0.5" w.c.
      • High Return Static + Low Supply Static = Restricted Return Ductwork
      • Low Return Static + High Supply Static = Restricted Supply Ductwork
    • Static Pressure Normal ⇒ Increase Blower Speed or Clean Blower Wheel

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Article ID: 237
Last updated: 23 Oct, 2020
Revision: 14
Access: Public
Views: 2282
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