Goodman Gas Furnace: GMPN

Re: Code 1 / Won't Ignite

Code 1 = 3 Failed Ignition Attempts

CHECKOUT:

1. Check Ignition Sequence

• If necessary, reset the furnace lockout by cycling high voltage or low voltage power.
• Initiate a call for heat from the thermostat and monitor the ignition sequence.
  • The inducer motor should start with no difficulty.
  • The pressure switch should close within a couple seconds of the inducer starting.
  • The glow plug should energize within 30 seconds of the pressure switch closing.
    • No Glow from Glow Plug → Step 3. Check Glow Plug
  • The gas valve should power and open within 20 seconds of the glow plug energizing.
    • Check for 24VAC across the two wires at the gas valve.
      • No Power → Step 4. Check Control Board Output
      • Power + No Ignition → Step 5.  Check Gas Pressure / Valve

2. Check Ignition

• Visually inspect the burners during ignition.
  • The burners should light smoothly with little or no delay from the glow plug to the flame sensor.
  • Make sure the flame sensor comes in good contact with the flame.
    • Burners Ignite Properly → Step 6.  Check Flame Sensor
    • Any Delay or Burners Not Igniting = Clogged Burners, Low Gas Pressure or Bad Gas Valve → Step 5.  Check Gas Pressure / Valve

3. Check Glow Plug

• Look for any visual cracks.
• Test resistance of the glow plug.
  • No Resistance = Bad Glow Plug
• Start an ignition sequence.
• Check for 120VAC power on the 2-wire plug feeding the glow plug during an ignition sequence.
  • No Power = Bad Ignition Control
  • Power Present + No Glow = Bad Glow Plug

4. Check Control Board Output

• Re-start the furnace with a call for heat from the thermostat.
• After the glow plug starts to heat-up, check for 24VAC from terminal 7 (Purple) of the molex plug on the control board to ground.
  • Approximately 15 - 20 seconds after powering the glow plug, the control board should send 24VAC power out terminal 7 to the gas valve.
    • No Power = Bad Control Board
    • Power at Board + No Power at Gas Valve = Tripped Limit ⇒ Check each manual-reset Roll-Out Limit (around the burners) and the Stack Limit (vent outlet).
      • If a roll-out is tripped, suspect and check for a Bad Heat Exchanger.
      • If the Stack Limit is tripped, suspect a Clogged or Restricted Vent.

5. Check Gas Pressure / Valve

• Inlet Gas Pressure
• Turn off power to the furnace and check the inlet gas pressure.
  • Minimum Pressure = 5" w.c. for Nat. gas, and 11" w.c. for propane.
  • Maximum Pressure = 15" w.c. (Excessive pressure may lock the gas valve closed).
    • Low Pressure = Bad Meter or Regulator
    • High Pressure = Bad or Wrong Regulator
• Re-apply power to the furnace and activate a call for heat.
• Make sure the inlet gas pressure stays above minimum when the gas valve energizes.
  • Pressure Drops Below Minimum = Bad Meter/Regulator or Restricted Gas Line
• Manifold Gas Pressure
• Activate a call for heat and monitor the manifold gas pressure during an ignition attempt.
  • Normal Pressure = 3 - 3.5" w.c. for Nat. Gas, 9 - 11" w.c. for LP
    • No Gas Pressure = Bad Gas Valve or Excessive Inlet Gas Pressure
    • Low Gas Pressure ⇒ Increase Manifold Gas Pressure
    • Normal Gas Pressure but No or Delayed Ignition = Clogged Burners ⇒ Remove burners and clean spreaders

6. Check Flame Sensor

• DO NOT clean the flame sensor before testing!
• On the multi-meter:
  • Switch the test leads to "COM" and "mA".
  • Set the meter on DC 200ù.
  • Check the reading when the burners ignite.
    • Minimum acceptable reading = 1 MicroAmp
      • Low Reading ⇒ Clean Flame Sensor & Re-check
      • Normal Reading (2 to 6 mA) but Shuts Off = Bad Control Board
  • MOVE SENSOR LEADS BACK TO "COM" and "V" BEFORE PROCEEDING!