Furnace error codes

Furnace lockout after an excessive number of ignition retries (3 total): flame was not established, or flame was lost after it was established.

Low stage pressure switch circuit is not closed.

Primary limit circuit is open. The chart lists insufficient air over the heat exchanger.

Flame was sensed with no call for heat.

Flame sense microamp signal is low.

Igniter circuit fault. The furnace fails to operate.

High stage pressure switch circuit is closed at the start of the heating cycle.

High stage pressure switch circuit is not closed.

Open fuse, with no furnace operation.

Auxiliary limit switch (condensate switch) is open. The furnace fails to operate.

Auxiliary limit switch in the blower compartment is open. The furnace fails to operate.

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

Flame was detected when it should not be present.

Open inducer limit switch, or open condensate pressure switch.

Open fuse. The control diagram in this installer's guide labels the low-voltage fuse as 5 amp.

Flame current is low, but still strong enough to allow operation.

Retry exceeded: flame was never sensed. One-hour lockout after 3 times.

Recycles exceeded: flame was sensed and then lost. One-hour lockout after 10 times.

Shorted pressure switch, 1st stage.

1st stage gas valve was not energized when it should be, and that fault was exceeded after 10 times.

Open pressure switch, 2nd stage.

Igniter fault: the igniter relay fails, or the igniter is open.

Open pressure switch, 1st stage.

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

Blower on after power-up. The blower runs for 90 seconds if the furnace is powered up during a call for heat, or if that call opens during the blower on-delay. The same guide's sequence says the amber LED flashes 12 during those 90 seconds, then stays on continuously if no fault is found.

Limit circuit lockout. The limit or flame rollout switch was open longer than 3 minutes, or 10 successive limit trips occurred during high heat. The control auto-resets after 3 hours. The manual says to see status code 33.

Ignition lockout. The system failed to ignite gas and prove flame in 4 attempts. The control auto-resets after 3 hours. The manual says to see status code 34.

Blower motor lockout. The blower failed to reach 250 RPM, or failed to communicate, within 30 seconds after being turned on, in two successive heating cycles. The control auto-resets after 3 hours. The chart says to see status code 41.

Gas heating lockout. The control will not auto-reset. The chart says to check for a mis-wired gas valve or a defective control valve relay.

Abnormal flame-proving signal. Flame is proved while the gas valve is de-energized. The inducer runs until the fault clears. The chart says to check for a leaky gas valve or a stuck-open gas valve.

Pressure switch did not open. The chart says to check for obstructed pressure tubing or a pressure switch stuck closed.

Secondary voltage fuse is open. The chart says to check for a short circuit in the secondary (24 V) wiring.

Model selection or setup error. The model plug PL4 is missing or incorrect, or setup switch SW1-1 or SW1-6 is in the wrong position. If 25 flashes only four times at power-up, the control is using the model stored in memory.

High-heat pressure switch or relay did not close, or it reopened. The chart says the control relay may be defective or the gas valve may be mis-wired, and it says to see status code 32.

Low-heat pressure switch did not close, or it reopened. If it stays open longer than five minutes, the inducer shuts off for 15 minutes before a retry. If it opens during the blower on-delay, the blower comes on for the selected blower off-delay.

Limit circuit fault. A limit, draft safeguard, flame rollout, or blocked-vent switch is open, or the furnace is in high-heat only after two successive low-heat limit trips. The blower runs for 4 minutes or until the switch remakes, whichever is longer. Open longer than 3 minutes becomes lockout 13.

Ignition proving failure. The control tries three more times before lockout 14. If the flame signal is lost during the blower on-delay, the blower runs the selected off-delay.

Gas valve fault on a Bryant 987MA modulating furnace. The modulating gas valve failed to respond to a command from the furnace control, or power to the gas valve electronics was interrupted.

Blower motor fault. The blower failed to reach 250 RPM, or failed to communicate, within 30 seconds after being turned on or within 10 seconds during steady-state operation.

Inducer motor fault on a Bryant 987MA modulating furnace. The inducer has not started within 20 seconds after a call for heat, the inducer RPM is outside its valid range, or the RPM signal was lost for 5 seconds during operation.

Low-heat pressure switch is open while the high-heat pressure switch is closed. The chart says to check the pressure tubing, low inlet gas pressure if a low-gas-pressure switch is used, mis-wired switches, and a low-heat switch stuck open.

Line voltage polarity is reversed, or, on twinned furnaces, the transformers are out of phase. The status table states the polarity fault. The rapid-flashing section is the twinning case.

Control circuitry lockout. The control auto-resets after a 1-hour lockout caused by a flame-sense circuit failure, a gas-valve relay stuck open, or a software check error. Reset power to clear the lockout. Replace the control if the code repeats.

No previous code. The service label says stored status codes are erased automatically after 72 hours.

Blower on after power-up. The service label calls this normal operation. The blower runs for 90 seconds if the furnace was powered up during a call for heat, or if that call opened during the blower on-delay.

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

Gas heating lockout. Control will NOT auto-reset.

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

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.

Control has 24 VAC power: a steady amber LED is not a fault code.

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

Status LED stays off: the service label says to check for 115 VAC at L1 and L2, and for 24 VAC at SEC-1 and SEC-2.

Grounding fault / poor neutral connection.

Open rollout switch.

Lost communication with the R-32 sensor: heating stops and only the fan runs because the furnace is in mitigation mode.

R-32 sensor reports a refrigerant leak: heating stops and only the fan runs while the furnace is in mitigation mode. The chart says normal operation returns once a leak is not detected and the 5-minute delay is over.

R-32 sensor fault: heating stops and only the fan runs while the furnace is in mitigation mode.

Blower current too low after the heat on-delay: the main blower is below the value the control expected, and the furnace goes to hard lockout.

A2L relay fault: heating stops and only the fan runs while the furnace is in mitigation mode. The fault is on the furnace control board.

Blower current too high during pre-purge: the main blower is above the value the control expected, and the furnace goes to hard lockout.

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

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

Pressure switch circuit is not closed.

Primary limit circuit is open.

Open fuse.

Flame sensed with no call for heat.

Low flame signal: flame sense microamp signal is minimal.

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

Gas valve is not energized when it should be.

Gas valve is energized when it should not be.

Internal faults or IRQ loss in control board.

Twin error. The twinning feature is not working. The chart says to check the wiring connections, then replace the integrated control board.

Inducer relay error. The furnace fails to operate, and the chart says to replace the integrated control board.

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.

Hard lockout: the rollout circuit is open, or it was open.

Low pressure switch failed open.

Limit switch circuit open. If the limit does not close within 3 minutes, the furnace goes into a 1-hour soft lockout.

Soft lockout: retries ran out and no flame current was sensed.

Restricted heat airflow: airflow is below the minimum, and the furnace is in a 1-hour soft lockout.

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

Main power polarity reversed. Switch line and neutral.

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

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.

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

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 closed while the inducer is off. This is a critical fault for gas heat. Cooling can still run. The code is present during a heat call before pre-purge.

Water circuit open. The control cannot see continuity between pins 1 and 2 of connector P4, so it does not see both water sensors. Gas heat will not run. Other modes, such as cooling, should.

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.

No valid model data on the memory card. This is a non-critical fault. The furnace should still operate, and d4 is displayed in standby.

No model data. This is a critical fault. The furnace will not operate in any mode, including a thermostat call.

Horsepower conflict on the memory card. The motor's horsepower does not match the card, but the model data in the furnace control does match the motor. This is a non-critical fault, shown in standby.

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.

Inducer and blower are not communicating: the service facts call this an internal control-board error between those two microprocessors.

Gas-valve relay fault, or 24 VAC at the 2nd stage valve: the control reports failed internal gas-valve relays, or voltage sensed at the 2nd stage gas valve.

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

Blower does not match the personality module: the motor horsepower or OEM identification differs from the value programmed on the module.

Personality module and control data are both corrupted.

Personality module missing: the control cannot read the information stored on the board.

No return signal from the blower: the integrated furnace control does not see the motor answer.

Control does not see its own send message: the integrated furnace control is not seeing the blower-communication send.

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

1st stage gas valve not energized: it failed 10 times in the same call for heat. The service facts say 24 VAC was not sensed on MVL those 10 times.

High-limit output relay is not closed when it should be. The service facts say 24 VAC was not sensed on HLO ten times.

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

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

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

2nd stage pressure switch PS2 is closed when it should be open. The service facts say the pressure switch is not the problem in most cases.

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.

Redundant high-limit relay stuck closed: the service facts call this an internal control-board error. The relay is closed when it should not be.

Flame was sensed when there was not a call for heat. The control turns on both the inducer motor and the supply air blower.

The main limit switch has opened and stayed open for more than five minutes. The manual says this is usually a failed blower motor or blower wheel. The control is in a hard lockout. Power has to be cycled off and on only after the problem is corrected.

The gas valve is energized with no call for heat. The main blower and the inducer blower run, and no ignition sequence starts, for as long as this condition exists.

The pressure switch is closed when it should be open. The control checks that the contacts are open at the start of each heat cycle and will not continue ignition if they are already closed.

The main limit switch has opened its normally closed contacts. The control runs the supply air blower and the inducer while the limit stays open.

The pressure switch contacts are open when they should be closed.

The flame could not be established during three trials for ignition. The furnace locks out for one hour and then restarts.

While the furnace was operating, the pressure switch opened four times during the call for heat. The furnace locks out for one hour and then restarts.

The flame was lost five times (four recycles) during the heating cycle. The furnace locks out for one hour and then restarts.

The normally closed rollout switch has opened. The rollout control is manually reset. The control enters a hard lockout, and power has to be cycled off and on only after the problem is corrected.

Reversed line-voltage polarity, a grounding problem, or reversed low-voltage transformer wires. Heating and cooling are both affected. The furnace will not start the ignition sequence until this is corrected.

Flame sense current is below 1.5 microamps. The manual's ignition-control levels put a normal flame sense current at about 3.7 microamps DC, the low-flame warning at 1.5 microamps, and the control lockout point at 0.1 microamps DC.