York Gas Furnace: TG9S/GY9S

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 pressure switch circuit is closed, the board will flash a Code 2.

► PS1 and PS2 are wired in series, so both switches would have to be closed to cause a Code 2.

► A Code 2 will typically keep the inducer motor from starting and the gas furnace from operating.

CHECKOUT:

1. Check Controller

• Check for 24VAC power from "W" to "C".
  • 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.

2. Check Pressure Switch Contacts

• PS1 Inducer Pressure
• DO NOT PULL WIRES OFF OF SWITCH - MAY RESET CONTACTS!
• Check for 24VAC from both sides of the switch to "C".
  • Power on both sides = Switch Closed
  • Power on only one side = Switch Open
• PS2 Condensate Switch
  • Check for 24VAC from both sides of the switch to "C".
    • Power on both sides = Switch Closed
    • Power on only one side = Switch Open

3. ADPS Switch Setting

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