HVAC Code Lookup

York Furnace Steady On (Any Color)

Hard lockoutShown as: LED lit solid, not flashing, in any color

Control failure. The board has detected an internal fault. On the TM8Y/TM9Y board an open 24V control fuse also produces a steady red LED.

Manual wording: “STEADY ON ANY COLOR: Control failure. Turn power to the furnace off and back on. If the fault code returns, the control board must be replaced. The control board is not field-repairable.”

Documented for: TG8S, TG9S, TM9E, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Internal control board failure
  2. Open 24 volt control fuse on the board (TM8Y / TM9Y)

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute, then back on once, to see if the code clears

When to call a technician

If the solid LED returns after one power cycle, the control board must be replaced. Johnson Controls states the board is not field-repairable, so this is a technician job.

A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other York codes