Lennox fault codes

Drive is enabled but stays at min Hz or 0 because analog / serial speed is missing.

2 plates

Flame with the valve off.

3 plates

Pressure switch is made with the inducer off.

3 plates

Draft not proven. On this 96% that is trap / PVC / collector — not a chimney.

3 plates

Airflow / overtemp.

3 plates

Flame containment. Hazard.

3 plates

Hardened 3-flash / 2-flash. Retries used up on draft.

3 plates

Failed to light / prove flame.

3 plates

Had flame, then lost it. Retries used up.

3 plates

L1/N reversed or ground missing.

3 plates

JADE LCD: ACT ERROR / ACT RANGE. Actuator did not follow command. Feedback pot off the shaft is the weekly.

2 plates

Indoor blower alarm / prove.

1 plate

HERM and/or FAN section out of rating. Single-stage Comfort dies this way all summer.

3 plates

Wrong charge method is as common as wrong charge.

3 plates

JADE LCD: CO2 / SENS ERR. DCV sensor failed or the 0–10 V input is floating. Damper holds open; compressor never runs.

2 plates

Drive or bus. Wall control loses the outdoor.

2 plates

Will not pull, chatters, or is welded.

5 plates

Mechanical cool did not prove.

1 plate

Mechanical cool did not prove.

1 plate

Float switch or tripped condensate opened 24V.

2 plates

Menu: last 10 stored codes.

2 plates

Device off the iComfort bus. Native, expected, first-class on SLP99.

4 plates

Line voltage below nameplate. Control waits; resumes ~5 s after voltage recovers.

2 plates

IFC does not see earth ground. Unit shuts down.

2 plates

Line voltage above nameplate.

2 plates

No clean 60 Hz. OEM: no 60 Hertz power.

2 plates

Secondary below ~18–30 V class. Control restarts if voltage recovers.

2 plates

Ground is present but dirty. Warning only — clears ~30 s after it recovers.

2 plates

IFC lost serial talk with the VS indoor blower (including a motor that never powered up).

6 plates

Programmed unit size does not match the motor horsepower the IFC sees.

2 plates

Unit size code is blank or invalid after a new IFC.

2 plates

Valve harness does not match what the IFC commanded.

2 plates

IFC thinks its valve relay contacts are shorted.

2 plates

High-fire solenoid will not drive. OEM: furnace runs first stage only for the rest of the call.

2 plates

Hot-surface ignitor circuit measures open.

4 plates

Ignitor open or trigger fault.

3 plates

Low-fire pressure path did not make.

4 plates

Low-fire prove failed. On this 80% that is chimney, inducer, common vent — not a drowned 96% trap.

1 plate

Modulating prove failed at that rate. Stat may say low/high PS even though the hardware is a band, not two EL296 discs.

2 plates

Low switch made with inducer off.

4 plates

High-fire prove failed.

5 plates

High switch made when it should be open.

4 plates

Low switch had closed, then opened mid-trial or in run.

4 plates

Could not finish PS calibration.

4 plates

Low PS did not close; IFC lit on high. OEM: not a separate high-fire repair.

5 plates

Flame is present but µA is below the run threshold.

4 plates

Weak µA or max retries with no flame current.

2 plates

Flame with valve off. Hazard.

4 plates

Limit / rollout string open. Open >3 min → E274.

6 plates

Airflow / overtemp. 5-flash on a flash SKU is still rollout.

1 plate

Leaving-air temperature above the gas-heat limit (DAT sensor).

2 plates

Never saw flame current.

4 plates

Max retries, no flame current (7-seg) or ignition lockout (flash).

1 plate

Last try died on a pressure switch.

4 plates

Ran, then draft dropped.

4 plates

Lost flame after it had proven.

4 plates

Hardened E250.

4 plates

Soft lockout after out-of-sequence flame. Same hazard family as E241.

2 plates

Failed ignitor or trigger circuit.

4 plates

VS heat CFM is below the minimum the IFC will allow for this firing rate.

2 plates

Indoor blower did not start — seized bearings / obstructed wheel class.

2 plates

Blower / module overtemp. IFC sheds or parks heat.

2 plates

Cooling or continuous-fan CFM is below the setting. Cutback / high-static warning.

2 plates

Start here when the hood is the complaint. Title 24 FDD classes: sensor, not-economizing, false-economizing, damper not modulating, excess OA.

2 plates

Drive has line voltage but will not run — the unit board never enabled it.

2 plates

Damper open past the commanded minimum with no economizer or DCV request.

2 plates

Menu: live flame current in µA on the 7-seg.

2 plates

Damper open with OA above changeover. Space hot, high OA bills, or wet coil.

2 plates

Indoor fan did not prove.

1 plate

Controller did not see blower current / pressure.

2 plates

Flame present then dropped, or µA too low to prove.

1 plate

JADE LCD: FREEZING. Mixed air below the low-limit. Damper drives shut; mechanical cool may lock.

2 plates

Keypad example: GF. Drive sees current to ground on the motor leads.

2 plates

Heat section did not prove.

1 plate

Heat did not prove.

1 plate

Outdoor HPS opened — coil circuit is dead. Not an inverter pressure fault and not an L-code.

5 plates

Still real on an inverter.

2 plates

Idle / heartbeat. Decimal blinks 1 Hz. Not a fault.

2 plates

Trial for ignition failed after the IGC retries.

1 plate

L5/L4-class faults on the drive.

2 plates

Heat-exchanger or supply limit opened.

1 plate

Drive is running too slow to close the prove switch, so the unit board reports fan fail. Reliatel example: Fan Fail with the drive still at min Hz.

2 plates

Suction dropped out the low-pressure switch.

2 plates

JADE two-line LCD: MA / SENS ERR. Mixed-air sensor failed. This one alarms immediately on power-up — others wait the 60-minute setup window.

2 plates

Damper is two-position (0 or 100) instead of tracking 2–10 V. Title 24 FDD class.

2 plates

OA is in the free-cooling window and the damper stayed shut. Title 24 FDD class.

2 plates

JADE LCD: OA / SENS ERR (or OA SYLK ERR). Outside-air thermistor failed or lost SYLK. Board thinks the roof is 20 °F or 120 °F.

2 plates

Keypad example: oC (Yaskawa) or OC. Output current trip. Locked rotor, dirty filters, or FLA set too low.

2 plates

Fan not turning. Compressor may still run and then HPS.

3 plates

Keypad example: oH. Drive thermal trip.

2 plates

Keypad example: ov (Yaskawa) or OU. DC bus high. Usually regen on decel, not a new drive.

2 plates

VS only. Stores cabinet / motor capacity in non-volatile memory.

2 plates

Keypad example: PF. Missing or imbalanced incoming phase.

2 plates

Three-phase monitor opened.

2 plates

JADE LCD: RA / SENS ERR. Return-air thermistor failed. Differential / enthalpy changeover compares OA to RA.

2 plates

Flame left the burner box.

1 plate

Supply or return smoke detector, or a firestat, has the unit locked out.

2 plates

Keypad example: Uv (Yaskawa) or LU. DC bus dropped. Incoming power or a missing phase.

2 plates

The indoor fan is a drive, not a contactor + cap. Type the keypad string: oC, Uv, ov, GF, oH, PF.

2 plates