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YP9C - Flashing Code 8

Article ID: 576
Last updated: 21 Nov, 2018

York Gas Furnace: YP9C

Re: Flashing Code 8

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


Qty Possible Causes:
2 Dirty Flame Sensor
Exhaust Leak in Cabinet


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.
    • 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 β‡’ 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 200ΓΉ.
    • 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 β‡’ Clean Flame Sensor & Re-check
    • CAUTION! Move meter leads back to "COM" and "V" before proceeding!
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Article ID: 576
Last updated: 21 Nov, 2018
Revision: 1
Access: Public
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