TG8S - Flashing Code 7

York 80% Gas Furnace: TG8S

Re: Flashing Code 7 / Error Code 7

Flashing Code 7 = Lockout due to ignition retries.

► Code 7 is a Hard Lockout that disables heat operation and must be reset by cycling power to the furnace or by turning the thermostat off and back on.

CHECKOUT:

1. Glow Plug Issue

Johnson Controls has issued a service letter regarding this issue.

• On 80% furnaces with the new "Glow Stick" glow plug there has been issue with the furnace intermittently failing to ignite.
• It appears that the gas doesn't always come into contact with the glow plug.
• The solution has been to Install a Honeywell GlowFly glow plug. This igniter is a little longer and wider which provides a larger surface area for ignition.

2. Check Glow Plug

• Look for any visual cracks.
• Use a meter to test resistance of glow plug.
  • No resistance = Bad Glow Plug
• Check for 120V power to the Glow Plug during an ignition sequence.
  • No Power = Bad Ignition Control
  • Power present but no glow = Bad Glow Plug

3. Check for Proper Ignition

• Visually inspect the burners during ignition.
• Burners should light with little or no delay from the glow plug to the flame sensor.
  • Make sure flame sensor comes in good contact with the flame.
  • Any delay or burners not igniting = Clogged Burners
  • Burners light properly → Step 4. Check Flame Sensor

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.
    • Minimum acceptable reading = 1 MicroAmp
      • Low Reading ⇒ Clean Flame Sensor & Re-check
      • Normal Reading (2 to 6 mA) but Shuts Off = Bad Ignition Control
  • MOVE SENSOR LEADS BACK TO "COM" and "V" BEFORE PROCEEDING!