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GY8S - Flashing Code 3

Article ID: 452
Last updated: 07 Mar, 2019

York 80% Gas Furnace: GY8S

Re: Flashing Code 3

Code 3 = Furnace Pressure Switch failed to close on a call for heat.

This gas furnace has a single pressure switch which monitors for proper venting.


Qty Possible Causes:
2 Bad Inducer Motor
1 Bad Pressure Switch
Clogged Pressure Port
Bad Vent Blower Wheel
Blocked Vent
Item Stuck in Inducer Motor


CHECKOUT:

1. Check Control Board


2. Check Inducer Motor

  • Start the furnace with a call for heat.
  • Observe and listen to the inducer motor.
    • Inducer motor hums but does not start:
      • Bad Inducer Motor or Capacitor
      • Item in Inducer ⇒ Remove inducer & check
    • Inducer motor does not attempt to start & shows Code 3 ⇒ Check for 115V power to inducer.
      • Power + No Inducer = Bad inducer Motor
      • No Power = Bad Control Board

3. Check Pressure Switch

  • Ensure the pressure switch hose is properly attached at both ends.
  • Switch Contacts
  • With the wires attached to the switch, check for 24VAC between each terminal of the switch and Common.
    • 24VAC On Both Sides = Switch Closed 
    • 24VAC On One Side Only = Open Switch ⇒ Use a pressure meter to check the Switch Pressure.
  • Switch Pressure
  • Remove the pressure hose from the Inducer Motor.
  • Connect a pressure meter to the Inducer Motor pressure port.
  • Compare actual pressure to the pressure rating on the switch.
    • Pressure Near or Below Rating = Clogged or Restricted Vent or Bad Vent Blower Wheel ⇒ Remove and Check Blower
    • Pressure Well Above the Rating + Open Switch = Bad Switch
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Article ID: 452
Last updated: 07 Mar, 2019
Revision: 10
Views: 36
Comments: 0