PT9 - Flashing Code 5

York Gas Furnace: PT9

Re: Flashing Code 5

Code 5 = Roll-out switch has opened its normally closed contacts or low voltage fuse blown.

• The control will operate the supply air blower and inducer while the open limit condition exists.

► The primary limit is wired in series with the roll-out limits, so an extended opening of the primary limit may also be interpreted by the control board as an open roll-out.

CHECKOUT:

1. Check Roll-Out Limits

• Initiate a call for heat by energizing W1.
  • Ignition sequence proceeds normally → Step 3. Check Burners
  • Code 5 ⇒ Continue 
• DO NOT ATTEMPT TO RESET ANY ROLL-OUT LIMITS YET!
• Check for 24VAC between both sides of each roll-out limit and "C".
  • No Power at Either Limit → Step 2. Check Primary Limit
  • Power on Both Sides = Limit Closed
  • Power on One Side Only = Limit Open
    • Attempt to reset any open limit(s) by pushing its reset button, then recheck for 24VAC.
      • Still Power on One Side Only = Bad Roll-Out Limit
      • Power on Both Sides → Step 3. Check Burners

2. Check Primary Limit

• Check for 24VAC between both sides of the primary limit and "C".
  • Power on Both Sides = Limit Closed → Step 3. Check Burners
  • Power on One Side Only = Limit Open
    • Open Limit + Cool Chamber = Bad Primary Limit
    • Open Limit + Hot Chamber → Step 4. Check Control Board/Blower Motor

3. Check Burners

• Observe the burners as the furnace ignites.
• Make sure all the burners light smoothly and no flame roll-out.
  • Roll-out before the blower starts = Clogged Heat Exchanger
• Observe the burners when the blower starts.
  • Roll-out or significant flame change when the burners start = Bad Heat Exchanger
  • No change in burner pattern → Step 4. Check Control Board/Blower Motor
  • Blower never starts + Code 4 → Step 4. Check Control Board/Blower Motor

4. Check Control Board/Blower Motor

• Check the blower motor operation in both Low and Hi fire (W1 & W2).
  • Low Fire
  • Blower Operates Normally ⇒ Check Hi Fire (W2).
  • Blower never starts or only starts when burners shut off on Code 4.
    • Reset furnace and Check for 120VAC between "Lo Heat" and Neutral after burner fire.
      • No Power = Bad Control Board
      • Power + No Blower Operation = Bad Blower Motor/Capacitor
  • Hi Fire
  • Blower Shuts Off on Hi Fire (W2).
    • Check for 120VAC between "Hi Heat" and Neutral.
      • No Power = Bad Control Board
      • Power + No Blower Operation = Bad Blower Motor/Capacitor