Goodman Heat Pump Won't Defrost

Goodman Heat Pump: GS13

Re: Won't Defrost

The Goodman GS13 Heat Pump uses a Time & Temperature Defrost Board.

• A defrost thermostat mounted to the outdoor coil closes at approximately 30 deg. and opens at approximately 60 deg.
• An adjustable setting on the board allows adjustment of the time between defrost cycles to either 30, 60 or 90 minutes.
• When the board receives 24VAC on the "Y" terminal the timer starts. When the compressor runtime exceeds the set defrost time, and the defrost thermostat is closed, a defrost cycle will be initiated.

CHECKOUT:

1. Check Operating Status

• Set the thermostat to call for heat.
• Ensure that the compressor and outdoor fan start and run properly.
  • Compressor & Outdoor Fan Ok → Step 3. Check Refrigerant Charge
  • No Outdoor Fan Operation → Step 2. Check Fan Motor

2. Check Fan Motor

• With the compressor operating, use a multi-meter to check for 230VAC power between the motor's Black and Red wires.
  • No Power = Bad Defrost Board or In Defrost Mode
  • Power but No Operation = Bad Fan Motor or Capacitor

3. Check Refrigerant Charge

Hook-up refrigerant gauges to the pressure ports on the unit.

• Blue ⇔"True Suction" Low Pressure
• Red ⇔ High Pressure (either refrigerant line)

• Monitor pressures as the system operates.
• DO NOT ATTEMPT TO ADJUST REFRIGERANT CHARGE IF THE OUTDOOR COIL IS FROZEN!

• If a Liquid-Line Sight Glass is installed, observe for bubbles in the sight glass (after the system has been operating for at least 5 min.)
  • Bubbles = Low Refrigerant Charge
• Low Pressure Issues
  • Low Suction + Low Discharge + Bubbles in Sight Glass + Expansion Valve Frosting = Low Refrigerant Charge
    • Try adding refrigerant through the Low Pressure gauge.
      • Suction and Discharge Pressures should gradually increase as refrigerant is added.
      • If the Discharge Pressure increases but the Suction stays low or drops = Bad Expansion Valve
  • Low Suction + Low Discharge + Clear Sight Glass + Expansion Valve Frosting = Bad Expansion Valve

4. Check Defrost Board

• Check for 24VAC between "C" and "R" on the defrost board.
  • No Power = Mis-wired Low Voltage
• Check for 24VAC between "C" and "Y" on the defrost board.
  • No Power on "Y" + Unit Operating = Stuck Contactor
• Check for 24VAC between "C" and "DFT" on the defrost board.
  • No Power = Defrost Stat Open (Not ready for defrost)
    • Cold Coil + Open Defrost Stat = Bad or Disconnected Defrost Stat
    • Warm Coil + Open Defrost Stat = Normal
      • ​​​​​​​It may be necessary to temporarily bypass the stat by placing a jumper across "R" and "DFT".
• Speed-up the timer by jumping the Test pins on the defrost board.
  • A defrost cycle should initiate within 5 seconds (Outdoor Fan Stops, Reversing Valve Switches to Cool Mode, Energizes Aux Heat).
    • Power on "R" and "Y" + No Defrost Cycle = Bad Defrost Board
    • Outdoor Fan Stops + Reversing Valve Doesn't Switch = Stuck Reversing Valve, Bad Rev Valve Coil or Loose Wiring to Coil