Trane
Polarity / power
LockoutLine / ground (door-card confirm)
If this door shows a polarity / line / ground token, treat L1/N and chassis ground. Confirm the exact code here.
Walk Polarity / power in Diagnose
4 plates — walk the one on the cabinet
First check
1 Hot and neutral at the IFC, not the disconnect
On Trane S9B1 polarity/ground is measured at the board. A correctly landed disconnect with a swapped whip at the IFC still throws this. Hot and neutral at the IFC.
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.
- Door switch, 24 V secondary, chassis ground.
- Door switch, 24 V secondary.