FieldBench
Lennox codes

Lennox

Cool

Lockout

Cool fail

Mechanical cool did not prove.

Walk Cool in Diagnose

Sign in for the next measurement

First check

1 Write the live code and watch one cycle

On Lennox LGT read Lennox current rooftop unit controller (not Landmark Prodigy) before you pull power. Write Cool exactly. Watch one full sequence and note which step dies. Economizer first, then contactor / HPS.

Expect: Call: Occupied / G starts the indoor fan. Y1 is cool. W is gas heat. They are different boards in the same box.

The rest of the walkthrough is Diagnose.

On the plates

  • Economizer first, then contactor / HPS.

Plates that use Cool