All furnace error codes

Limit circuit lockout: a limit or flame rollout switch was open longer than 3 minutes. Control auto-resets after 3 hours (see code 33).

Ignition lockout: system failed to ignite gas and prove flame in 4 attempts. Control auto-resets after 3 hours (see code 34).

Gas heating lockout. Control will NOT auto-reset.

Abnormal flame-proving signal: flame is proved while the gas valve is de-energized. Inducer runs until the fault is cleared.

Pressure switch did not open.

Secondary voltage (24 V) fuse is open.

Low (LPS) or high (HPS) pressure switch did not close or reopened.

Limit circuit fault: a limit or flame rollout switch is open. Becomes lockout 13 if open longer than 3 minutes.

Ignition proving failure: flame not sensed during trial for ignition. Control tries 3 more times before lockout 14.

Control circuitry lockout. Auto-resets after 1 hour.

Line voltage (115 VAC) polarity reversed. If twinned, check 24 V transformer phasing.

Open rollout switch.

Grounding fault / poor neutral connection.

Primary limit circuit is open.

Pressure switch circuit is closed at the start of the heating cycle.

Pressure switch circuit is not closed.

Flame sensed with no call for heat.

Furnace lockout after too many ignition retries (3 total): flame failed to establish or was lost after establishment.

Low flame signal: flame sense microamp signal is minimal.

Open fuse.

Gas valve is energized when it should not be.

Polarity of 115 volt AC is reversed, or poor unit ground.

Internal faults or IRQ loss in control board.

Gas valve is not energized when it should be.

Problem with igniter circuit.

Igniter open.

Improper main ground, OR line voltage below 90 volts. Control will not respond to a heat call until voltage rises above 95 volts.

Watchguard 1 hour: burners failed to ignite or lost flame 5 times during a single heating demand.

Circuit board failure or control wired incorrectly.

Main power polarity reversed. Switch line and neutral.

Pressure prove switch open, OR blocked inlet/exhaust vent, OR pressure switch closed before the combustion air inducer started.

Rollout switch open, OR 12-pin connector improperly attached.

Low flame signal: measures below 1.5 microamps. Replace flame sense rod.

Flame sensed without gas valve energized.

Primary or secondary limit switch open. Limit must close within 3 minutes or the unit goes into 1-hour Watchguard.

One-hour lockout, caused by repeated failed ignition (11), water sensed (59), dead blower (61), internal fault (93), flame lost 5 times (13) or unexpected flame (14).

Failed ignition. After four failed attempts the control enters one-hour lockout (10).

Low flame sense: flame sense current is weak or marginal. Furnace keeps running.

Flame lost after established.

Flame present with gas valve off. Extremely critical; furnace will not operate.

Open fuse, usually from a 24 VAC short to common or ground.

Over-temperature (rollout) switch open: flames rolled out of the heat exchanger into the burner compartment.

Low pressure switch closed with inducer off.

Low pressure switch open with inducer on high speed.

Low pressure switch open with inducer on low speed.

High pressure switch open with inducer on high speed; furnace may drop to low fire.

Water sensed in the collector box; gas heat will not run.

Blower fault, blower can still run: blower at max speed/torque or temperature limit because static pressure is too high.

Blower fault, motor cannot run. Furnace will not operate in any mode.

Loss of the IRQ or other internal failures (internal furnace control error).

Open limit: main thermal limit, flame rollout switch, or reverse airflow switch.

Flame detected when it should not be present.

Voltage reversed polarity or bad grounding.

Low flame current, but still strong enough to allow operation.

Open inducer limit switch or condensate pressure switch.

Open fuse: the onboard 5 amp fuse is open or missing.

Retry exceeded: flame never sensed after 3 ignition tries in one call for heat. One-hour lockout.

Recycles exceeded: flame sensed then lost 10 times (or PS1 open 10 times) in one call for heat. One-hour lockout.

Shorted pressure switch, 1st stage: PS1 is closed when it should be open.

Open pressure switch, 1st stage: PS1 is open when it should be closed.

Open pressure switch, 2nd stage: PS2 is open when it should be closed.

Igniter relay fault or igniter open/shorted.

1st stage gas valve (MVL) is energized when it should be off.