York Heat Pump: ERC

Re: Outdoor Unit Not Running

The indoor blower is operating, but the outdoor unit fan and compressor are not running.

CHECKOUT:

1. Check High Voltage Power & Contactor

• Check for 230VAC inlet power across L1 and L2 of the compressor contactor.
  • No Power ⇒ Check Disconnect and Breakers
    • Check for a "Short-to-Ground" before checking breaker!
• Check to see if the compressor contactor is pulled-in.
  • Not Pulled-In → Step 2. Check Low Voltage
  • Pulled-In + Inlet Power + Not Running = Bad Contactor or Bad Capacitor
    • Check for 230VAC on the leaving side of the contactor.
      • Power In + No Power Out = Bad Contactor
      • Power Out + Not Running ⇒ Check for a Bad Capacitor
        • Motor and Compressor may both be off on over-temperature

2. Check Low Voltage Power

• Ensure the thermostat is calling for either heating or cooling.
• At the defrost control board, check for 24VAC between "R" and "C".
  • No Power = Bad Transformer or Loose Wiring
• Check for 24VAC between "Y" and "C" on the defrost board.
  • No Power = No Call from the Thermostat ⇒ Recheck Stat
    • Look for a Condensate Overflow Switch at the air handler.
• Check for 24VAC at the compressor contactor coil.
  • 24V Power Present but not Engaged = Bad Contactor
  • No Power at Contactor + Power on "Y" = Control Board Lockout or Bad Defrost Control
    • Attempt to reset the control by jumping the "Test" pins. 
      • Unit Starts → Step 3. Check Refrigerant Pressures
      • Unit Doesn't Start ⇒ Check for an open safety circuit on "Switch" terminals.
        • Safety Open → Step 3. Check Refrigerant Pressures
        • Safety Closed + Won't Engage = Bad Defrost Board

3. Check Refrigerant Charge

• Hook-up refrigerant gauges to the unit and observe pressure readings.
  • High Pressure Switch should open above 450 psig.

4. Test Safety Circuit

• Disconnect the two wires from the defrost board "Switch" terminals.
• Check resistance through the safeties.
  • Pressures Normal + Open Safety = Bad Pressure Switch