York Heat Pump: Yorkguard IV & Yorkguard V

Re: Flashing Code 4 / Compressor Won't Run

Code 4 = Low Compressor Discharge Temperature

• Code 4 is sometimes listed as "Compressor Not Operating", as this is one of the more likely causes. (see Possible Causes below)

The Yorkguard IV & V have the same functionality for a Code 4:

• 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 Code 4 lockout which disables compressor operation.

CHECKOUT:

1. Check Outdoor Unit

• Make sure the thermostat is set correctly and calling for heat or cool.
• Remove the access panel of the outdoor unit.
  • Compressor & Outdoor Fan Operating → Step 5. Check Pressures & Temperatures
  • Compressor Not Operating ⇒ Check for 230V inlet power on the compressor contactor.
    • No Power → Step 2. Check Compressor/Capacitor
    • Power Present ⇒ Check Diagnostic Light on Board
      • Diagnostic Present ⇒ Reset the control by momentarily removing "R" and "Y" from the board. Short the Test pins if necessary to speed-up the ASCD timer.
        • System Operates → Step 5. Check Pressures & Temperatures
        • System Doesn't Operate → Step 4. Check Contactor

2. Check Compressor/Capacitor

• Pull the service disconnect switch.
• Check for Short
• Check for resistance between each leaving leg of the compressor contactor & ground.
  • Any Resistance = Electrical Short ⇒ Remove the wires at the compressor terminals and check the compressor seperately.
  • No Resistance/Short ⇒ Check the Compressor Windings
• Check Compressor Windings
• Remove all three compressor leads from the contactor & capacitor.
• Check resistance between each lead (C & S), (C & R), (S & R).
  • Resistance Between All → Step 3. Check Breaker
  • No Resistance Between (C & S) and (C & R) = Over-Heated Compressor, Burnt Compressor Terminal or Bad Compressor → Check Compressor Temperature & Terminals.
  • Any Other Missing Resistance = Burnt Compressor Terminal or Bad Compressor ⇒ Check Compressor Terminals.
• Check Starting Amps
• ​​​​​​​With winding resistance correct, restart the unit while monitoring compressor amperage.
  • ​​​​​​​Compressor Pulls High Amperage + Does Not Start ⇒ Remove power by pulling disconnect and check capacitor.
    • ​​​​​​​Capacitor OK ⇒ Add a Hard-Start Capacitor
      • ​​​​​​​Still Won't Start = Bad Compressor

3. Check Breaker

• 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
  • Unit Operates Normally → Step 5. Check Pressures & Temperatures

4. Check Contactor

• Check the condition of the compressor contactor.
  • Contactor Pulled-In + No Compressor Operation ⇒ Check for 230V across the leaving legs of the compressor contactor.
    • Inlet Power + Outlet Power + No Compressor Operation = Over-Heated Compressor or Burnt Compressor Terminals ⇒ Check compressor temperature & terminals.
    • Inlet Power + No (or low) Outlet Power = Bad Contactor
  • ​​​​​​​Contactor Not Pulled-In ⇒ Check for 24VAC across the contactor coil.
    • ​​​​​​​24VAC Present + Not Pulled-In = Bad Contactor
    • No 24VAC Present ⇒ Re-check thermostat & diagnostics.

5. 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 (either refrigerant line)
• Re-apply power to the outdoor unit.
• Start the compressor with a call for heating from the thermostat.
• Observe refrigerant pressures as the system operates.
  • Allow the system to operate for at least 5 - 10 minutes.
    • Normal R-22 Pressures = 25 to 65 psig Suction, 150 to 270 psig Head.
    • Normal R410A Pressures = 85 to 130 psig Suction, 200 to 400 psig Head.
• Hook an insulated thermistor to the discharge line and check temperature.
  • Normal discharge temperature = 130 to 160 deg.​​​​​​​

6. 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 sensed temperature to the actual compressor discharge temperature.