York
9 red
LockoutReversed polarity / grounding
L1/N or chassis ground.
Walk 9 red in Diagnose
5 plates — walk the one on the cabinet
First check
1 Hot and neutral at the IFC, not the disconnect
On York TM8T polarity/ground is measured at the board. A correctly landed disconnect with a swapped whip at the IFC still throws this. Hot/neutral at the IFC, burner ground.
Expect: L1 hot, N neutral, ~120 VAC L1 to N, ~0 VAC N to ground.
The rest of the walkthrough is Diagnose.
On the plates
- Hot and neutral at the IFC, not just the disconnect.
- Burner box to IFC ground screw. Painted screw, missing star washer.
- Flame probe not shorted to chassis.
- Hot/neutral at the IFC, burner ground.