FieldBench
Lennox codes

Lennox

9 flash

Lockout

Polarity

L1/N reversed or ground missing.

Walk 9 flash in Diagnose

3 plates — walk the one on the cabinet

First check

1 Hot and neutral at the IFC, not the disconnect

On Lennox ML180 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. Chassis 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. Chassis ground. Flame sense will not work reversed.
  • Hot/neutral at the IFC. Chassis ground.

Plates that use 9 flash

Same number, other makers

9 flash on Lennox is not the same code on these plates.