York Gas Furnace: PT9 Re: Flashing Code 3 Code 3 = The 1LP pressure switch contact did not close during 1st stg heat operation, or the 2LP pressure switch contact did not close during 2nd stg heat operation ► The 1LP switch is typically rated for 0.75" w.c. and the 2LP switch is typically rated...

York Gas Furnace: PT9 Re: Flashing Code 4 Code 4 = Main limit switch has opened its normally closed contacts. The control will operate the supply air blower and inducer while the open limit condition exists. ► If the limit switch has not closed within five minutes, the control will assume...

York Gas Furnace: PT9 Re: No Heat - Flashing Code 7 Code 7 = Flame could not be established. This no-light condition occurred 3 times (2 retries) during the call for heat before locking out. ► The furnace will lock out for one hour and then restart. Qty Possible Causes: ...