TM9Y - Flashing Code 3

York Gas Furnace: TM9Y

Re: Flashing Code 3

Code 3 = The normally open (PS1 or PS3) pressure switch contact did not close after the inducer was energized.

► This is a "Soft Lockout" which will automatically reset after 1 hour.

► There are 3 pressure switches on this furnace. PS1 (1st Stage Switch usually .90") and PS3 (Condensate Switch usually .20") are wired in series to the pressure switch input. 

► The PS2 (2nd Stage Switch) wires in separately and will cause a Code 13.

CHECKOUT:

1. Check Inducer Motor Operation

• Start the furnace with a call for heat from the thermostat.
• Observe and listen to the inducer motor operation.
  • Inducer Motor Starts → Step 2. Check Pressure Switch
  • Inducer motor hums but does not start:
    • Bad Inducer Motor or Capacitor
    • Item in Inducer or Melted Blower Wheel ⇒ Remove inducer & check
  • Sound of water "slurshing" = Water in Inducer ⇒ Remove the Inducer, pour out water, re-install inducer → Step 3. Check Condensate Drainage
• Listen for sounds of water in the vent piping (near the furnace and at the vent termination).
  • If water is gurgling in the vent, look for sags or low spots in the vent piping that will hold water.
    • Pipe must have constant slope back toward furnace.

2. Check Pressure Switches

• PS1 (1st Stage Switch)
• Check for 24VAC between "C" on the terminal block and the Blk/Org wire on PS1.
• Check for 24VAC between "C" on the terminal block and the Wht wire on PS1.
  • Power On Both Sides = Switch Closed ⇒ Check PS3 Switch
  • Power on One Side Only = Switch Open ⇒ Check PS1 Pressure (below)
• PS3 (Condensate Switch)
• Check for 24VAC between "C" on the terminal block and the Wht wire on PS3.
• Check for 24VAC between "C" on the terminal block and the Red/Grn wire on PS3.
  • Power On Both Sides = Switch Closed
  • Power on One Side Only = Switch Open ⇒ Check PS3 Pressure (below)
• Check PS1 Pressure
  • Use a pressure meter to check the pressure at the PS1 switch.
    • Watch for water in the pressure switch hoses.
  • Compare actual pressure to pressure rating on the switch.
    • Pressure Near or Below Rating = Clogged or Restricted Vent
    • Pressure Well Above Rating + Open Switch = Bad Switch or Water in Switch
      • Water in Switch is usually caused by a mis-run pressure switch hose.
• Check PS3 Pressure
• Use a pressure meter to check the pressure at the PS3 switch.
• Compare actual pressure to pressure rating on the switch.
  • Pressure Near or Below Rating = Blocked Drain
  • Pressure Well Above Rating + Open Switch = Bad Switch

3. Check Condensate Drainage

• Check the Robber Drain Coupling on the inducer outlet.
  • On horizontal runs, make sure the drain outlets are pointed slightly down-hill.
  • Remove drain hoses.
    • Water running out of coupling = Clogged Drainage
• Check drain hoses from inducer and/or collector box.
  • Make sure all drain hoses are clear and have a downward slope.
• ! Make sure there is an "Air-Gap" in the PVC drain immediately upon exiting the furnace !
  • Any trap after the collector box before an air gap will cause drainage issues.
• In extreme cold conditions, be cautious of frozen drains.