Goodman Heat Pump: GSZ14
Re: Defrost Problem, Outdoor Coil Frozen
The Goodman GSZ14 Heat Pump uses a Time & Temperature Defrost Board.
► There are two different defrost boards used on these models.
- PCBDM101 = Simple Time & Temperature Defrost Board
- PCBDM133S = Advanced Time & Temperature Defrost Board with Extra terminals: "Cont" = Output to Contactor, "PS1" & PS2" = Pressure Switch Inputs.
| Qty |
Possible Causes: |
| 2 |
Bad or Disconnected Defrost Stat |
|
Bad Defrost Board |
|
Low Refrigerant Charge |
|
Bad Cond Fan Motor / Capacitor |
|
Mis-Located Defrost Stat |
|
Stuck Reversing Valve |
|
Defrost Timer Set Too Long |
CHECKOUT:
1. Check Operating Status
- Set the thermostat to call for heat.
- Ensure that the compressor and outdoor fan start and run properly.
2. Check Fan Motor
- With the compressor operating, use a multi-meter to check for 230VAC power between the motor's Purple and Black wires.
- No Power = Bad Defrost Board or In Defrost Mode
- Power + 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 Pressure Port
- Red ⇒ High Pressure Port (Either refrigerant line)
- Monitor pressures as the system operates.
| Normal Pressure Range |
| Refrigerant |
0-30 Deg O/D |
30-50 Deg O/D |
| R410A |
- 70-100 Suction
- 250-320 Discharge
|
- 100-135 Suction
- 250-375 Discharge
|
- Low Pressure Issues
- Low Suction + Low Discharge + 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 + High Discharge + 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.
- Check for 24VAC between "C" and "DFT" on the defrost board.
- Power = Defrost Stat Closed, Ready for Defrost
- No Power = Defrost Stat Open, Not Ready for Defrost
- Cold Coil + Open Defrost Stat = Bad or Disconnected Defrost Stat
- Warm Coil + Open Defrost Stat ⇒ 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.
- No Defrost Cycle = Bad Defrost Board
- Initiates Defrost + Terminates Quickly = Wrong Stat Location (Must be a coil feeder line between the metering device and coil)
- Normal Defrost Cycle ⇒ Check refrigerant pressures in defrost mode: Should come-up to approx. 300-350psi (Head) and at least 100psi (Suction) to terminate.