PHU - Flashing Code 2

Gas Furnace: PHU

Re: Flashing Code 2

(Assuming original control board)

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 inducer motor from starting and the gas furnace from operating.

Qty	Possible Causes (From Most to Least Likely):
1	Bad Pressure Switch
1	Inducer Fan Stuck On (Bad Control Board)
	ADPS Switch Set Too Low

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

DO NOT PULL WIRES OFF OF THE SWITCH - MAY RESET CONTACTS!
Check for 24VAC from both sides of the switch to "C".
- Power on Both Sides = Switch Closed
- Power on One Side Only = Switch Open

3. ADPS Switch Setting

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