GMPN - Flashing Code 2

Goodman Gas Furnace: GMPN

Re: Flashing Code 2

Code 2 = Pressure switch stuck closed

The furnace pressure switch should only close when the inducer fan output is energized. If control board is not energizing the inducer fan output and the switch is closed, the board will flash a code 2.

► A Code 2 will typically keep the gas furnace from operating.

CHECKOUT:

1. Check Controller

• Check for 24VAC power from "W" to Gnd.
  • Inducer fan should not be operating with no power on "W".
    • Inducer may continue to run for "post-purge" after a call for heat for up to 30 seconds.
    • Inducer may also run if a limit is tripped.
      • Inducer Running + No Limits Tripped + No Call for Heat = Bad Control Board

2. Check Pressure Switch Contacts

• DO NOT PULL WIRES OFF OF SWITCH - MAY RESET CONTACTS!
• Check for 24VAC from both sides of the switch (YEL) toGnd.
  • Power on both sides = Switch Closed
  • Power on only one side = Switch Open

3. Check Vent Pressure

• Hook a pressure gauge to the pressure switch hose.
• Operate the furnace in heating mode for at least 2 minutes.
• De-activate a call for heat (inducer motor should shut off within 30 seconds)
• Check negative pressure on switch with the inducer motor off. (should go to 0" w.c.)

4. ADPS Switch Setting

• The ADPS switch will sometimes fail to re-open when set for a low setting.