York Package Gas/Electric: PCG4

Re: Flashing Code 7

Code 7 = Failure to Sense Flame (3 Failed Ignition Attempts)

CHECKOUT:

1. Check Ignition Sequence

• Initiate a call for heat from the thermostat and monitor the ignition sequence.
  • 1. The inducer motor should start with no difficulty.
  • 2. The pressure switch should close within a couple seconds of the inducer starting.
  • 3. The Gas Valve should open and the Sparker start sparking once the pressure switch closes.
    • No Spark → Step 2. Check Sparker
    • Sparks + Fails to Ignite → Step 3. Check Ignition

2. Check Sparker

• Turn off power to the furnace.
• Remove the Spark Electrode from the burner compartment.
• Check to make sure the Spark Electrode is not broken or badly corroded.
• Check the Spark Wire to make sure it is not damaged.
  • Spark Electrode & Wire OK ⇒ Check for 24VAC at the Gas Valve during an ignition attempt.
    • 24VAC at Gas Valve + No Spark = Bad Control Board

3. Check Ignition

• Visually inspect the burners during ignition.
  • The burners should light smoothly with little or no delay from the Spark Electrode to the flame sensor.
  • Make sure the flame sensor comes in good contact with the flame.
    • No Ignition, Delayed Ignition or Not All Burners Igniting = Clogged Burners, Low Gas Pressure or Bad Gas Valve → Step 4.  Check Gas Pressure / Valve
    • All Burners Ignite Properly → Step 5. Check Flame Sensor

4. Check Gas Valve / Pressure 

• Restart a call for heat and check for 24VAC across the two wires at the Gas Valve at the point of Ignition.
  • No Power = Bad Ignition Control
  • Power + No Ignition ⇒ Check Gas Pressure (below)
• Check Inlet Gas Pressure
  • Minimum Pressure = 5" w.c. for Nat. gas, and 10" w.c. for LP.
    • Low Pressure = Gas Supply Issue
  • 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 = Gas Supply Issue
• Check Manifold Gas Pressure
  • Normal Pressure = 3 to 3.5" w.c. for Nat. Gas, 9 to 11" w.c. for LP.
  • Activate a call for heat and monitor the manifold gas pressure during an ignition attempt.
    • No Gas Pressure = Bad Gas Valve
    • Low Gas Pressure ⇒ Attempt to Increase Manifold Gas Pressure
      • Won't Increase = Bad Gas Valve
    • Normal Gas Pressure + No or Delayed Ignition = Clogged Burners ⇒ Remove burners and clean spreaders

5. Check Flame Sensor

• Check the flame sensor reading when the burners ignite.
  • Normal Reading = 2 to 6 mA
  • Minimum acceptable reading = 1 MicroAmp
    • Low Reading = Dirty Flame Sensor ⇒ Clean the Flame Sensor & Re-check
• CAUTION! Move meter leads back to "COM" and "V" before proceeding!