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TM9Y - Flashing Code 9

Article ID: 705
Last updated: 20 Apr, 2022

York Gas Furnace: TM9Y

Re: No Heat or Cool - Flashing Code 9

Code 9 = Indicates reversed line voltage polarity, reversed low voltage wiring, or Grounding problem

Qty Possible Causes:
1 Loose Ground
Missing Ground
Reversed Line Voltage ("Hot" on white)
Reversed Low Voltage
Loose "Neutral" Wire
Bad Control Board


CHECKOUT:

1. Check Grounding & Power

  • Inspect the incoming power for a connected Ground wire.
  • Check voltage from "Neutral" to the grounded furnace cabinet.
    • Any voltage reading = Improper Ground or Reversed Line Voltage
      • Check voltage from "Hot" to the grounded furnace cabinet.
        • No Voltage = Reversed Line Voltage
        • Partial Voltage = Improper Ground

2. Check Neutral

  • After confirming a good "Ground", check voltage from "Hot" to the grounded furnace cabinet.
  • Compare voltage from "Hot" to "Neutral".
    • Low voltage between "Hot" and "Neutral" = Loose "Neutral" Wire
      • Look for a loose or burnt Neutral connection between the furnace and power source.

3. Check Low Voltage Polarity

  • Turn off power to the furnace.
  • Try reversing the two secondary (low voltage) wires at the furnace transformer.
  • Re-apply power to the furnace.
    • ​​​​​​​Still Code 9 ⇒ Suspect a Bad Control Board
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Article ID: 705
Last updated: 20 Apr, 2022
Revision: 1
Views: 16
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