York 90% Gas Furnace: P3UR

Re: Flashing Code 6

Code 6 = Multiple Pressure Switch Openings on a call for heat.

CHECKOUT:

1. Check Venting

• Start the furnace with a call for heat.
• Observe and listen to the inducer motor.
  • Sound of Water "slurshing" = Water in Inducer ⇒ Remove Inducer, pour out water, re-install inducer → Step 3.  Check Condensate Drainage
• Listen for sounds of water in the vent piping (at the furnace and at the vent termination).
  • If water is gurgling in the vent, look for low spots that will hold water.
    • The vent piping must have a constant slope back toward the furnace.

2. Check Pressure Switch

• Make sure there are no sags in the pressure switch hoses that could hold water.
• Switch Pressure
• Use a pressure meter to check the pressure at the 1LP switch.
  • Must check positive & negative pressure together (differential pressure).
• Compare actual pressure to the pressure rating on the switch.
  • Pressure Near or Below the Switch Rating (0.90" w.c.) = Vent/Intake Issue ⇒ Check the negative pressure at the inducer and burner box individually.
    • Inducer Negative Pressure Low = Vent or Drain Problem or Inducer Problem ⇒ Remove inducer & check for obstructions or damaged wheel.
    • Burner Box Negative Pressure High = Intake Problem ⇒ Remove the burner box cover to see if pressure improves.
  • Pressure Well Above Rating + Open Switch = Bad Switch or Water in Switch

3. Check Condensate Drainage

• There are three drains that tie-in to a factory drain trap.
  • Vent Outlet
  • Inducer Motor
  • Collector Box
• Remove each drain hose individually.
  • Water running out of Drain = Clogged Drainage
• Remove the drain trap and flush-out at a sink.
• Check the main drain line.
  • In extreme cold conditions be cautious of Frozen Drains.