York Gas Furnace: YP9C

Re: Flashing Code 8

Code 8 = Flame was established but then lost 5 times.

CHECKOUT:

1. Check Ignition Sequence

• If the furnace is running, turn the thermostat off and allow the furnace to cool and the blower to stop operating.
• Initiate a call for heat from the thermostat and monitor the ignition sequence.
  • 1. The inducer motor ramps-up to close the pressure switch.
  • 2. The inducer motor ramps-down to open the pressure switch.
  • 3. The inducer motor ramps-up to close the pressure switch again.
  • 4. The control board powers the glow plug.
    • No Glow from Glow Plug → Step 2. Check Glow Plug
  • 5. The gas valve should open within 20 seconds of the glow plug energizing.

2. Monitor Burner Operation

3. Check Gas Pressure / Valve

• Inlet Gas Pressure
• Turn off power to the furnace and close the gas safety shut-off valve.
• Hook-up a gas pressure gauge to the inlet test port of the gas valve.
• Open the gas safety shut-off and check gas pressure.
  • Minimum Pressure = 5" w.c. for Nat. gas, and 11" w.c. for propane.
    • Low Pressure = Bad Meter or Regulator
• Re-apply power to the furnace and activate a call for heat.
• Make sure the inlet gas pressure stays above minimum when the gas valve energizes.
  • Pressure Drops Below Minimum = Bad Meter/Regulator or Restricted Gas Line
• Manifold Gas Pressure
• Turn off power to the furnace and close the gas safety shut-off.
• Move the gas pressure gauge to the manifold (leaving) test port on the gas valve.
  • CAUTION! Be sure to put the plug back in the inlet test port before proceeding!
• Open the gas safety shut-off valve and re-apply furnace power.
• Activate a call for heat and monitor the manifold gas pressure during an ignition attempt.
  • No Gas Pressure = Bad Gas Valve
  • Gas Pressure + No or Delayed Ignition = Clogged Burners ⇒ Remove burners and clean spreaders
• ONLY ADJUST MANIFOLD PRESSURE AT Hi-FIRE!

4. Check Flame Sensor

• On the multi-meter:
  • Switch the test leads to "COM" and "mA".
  • Set the meter on DC 200ù.
  • Disconnect the wire from the flame sensor.
  • Place one meter lead on the flame sensor terminal and the other on the flame sensor wire.
  • Check the reading when the burners ignite.
    • Normal Reading = 3.7 mA
    • Low Level Warning = 1.5 mA
    • Lockout Point = 0.1 mA
      • Low Reading = Dirty Flame Sensor ⇒ Clean Flame Sensor & Re-check
  • CAUTION! Move meter leads back to "COM" and "V" before proceeding!