Bryant Furnace 33 Error Code: Meaning, Causes & Fix
Limit circuit fault — a limit switch or flame rollout switch in the limit circuit is open. The blower runs for 4 minutes or until the open switch remakes, whichever is longer; open longer than 3 minutes, the code changes to lockout 13; remade sooner, 33 keeps flashing until the blower shuts off. The rollout switch requires manual reset.
Code 33 is Bryant's overheating-and-rollout report, with identical wording across the whole Bryant line — limit or flame rollout switch open, blower runs 4 minutes or until the switch remakes, 3 minutes to lockout 13 — printed on the single-stage 340AAV, 330JAV and 393AAV service labels, in the 577D control section, and in the variable-speed 355MAV guide. The limit circuit is a series string of safety switches watching the heat exchanger and the burner compartment. The main limit opens when the air around the exchanger gets too hot — which on a gas furnace almost always means heat is being made faster than air carries it away. The flame rollout switch watches the burner box instead: it opens when flame or hot gas escapes where it should never be, and unlike the main limit it does not remake on its own — it is a manual-reset device, and Bryant's 355MAV caution is blunt about the order of operations: correct inadequate combustion-air supply or component failure BEFORE resetting the switch. The control's behaviour while 33 shows is deliberate cooling, not confusion: burners off, blower running a full 4 minutes (or until remake, whichever is longer) to pull stored heat out of the exchanger. The variable-speed generation adds one clause the older labels do not print: on the 355MAV, 33 also reports the furnace operating in high-heat-only mode after 2 successive low-heat limit trips. Bryant's own proof test shows the code doing its designed job: gradually block the return air on a running furnace, and the moment the limit shuts the burners off, a 33 appears.
What causes the 33 code on a Bryant furnace?
Dirty filter or restricted duct system
First on Bryant's check list for 33 on every label. A loaded filter, closed or blocked registers and returns, or an undersized or crushed duct run starves the heat exchanger of airflow, and the limit opens to protect it.
Blower failure: defective motor or capacitor, loose blower wheel, wrong speed tap
Bryant lists the blower family together on the 340AAV label: defective blower motor or capacitor, a loose blower wheel slipping on its shaft, the blower set on an incorrect speed tap. If the air does not move, the limit finds out first.
Furnace firing too hard: input rate set too high
Also on Bryant's lists (340AAV: 'input rate to furnace set too high'; 355MAV: 'improper low-heat gas input adjustment', 'stuck high-heat solenoid in gas valve'). A furnace making more heat than its rating — or stuck on high fire — overheats even with honest airflow. Firing-rate work is gas work: technician only.
Restricted vent, improper vent sizing, excessive wind
The vent-side entries on Bryant's 33 list. A restricted or wrongly sized vent, or wind pressure fighting the termination, degrades combustion and draft and can push burner-compartment temperatures up until a switch opens.
Inadequate combustion air supply — the rollout branch
Bryant ties this cause to the flame rollout switch specifically: starved combustion air makes flame roll out of the burner opening instead of drawing cleanly in, the rollout switch (or its fuse link) opens, and it stays open until a human resets it or replaces the link — after the air problem is corrected.
Defective switch or connections — and, on variable-speed models, the limit's own mounting
Last on Bryant's lists, as it should be: a failed limit or rollout switch or its connections. The 355MAV adds two items the older labels do not carry — the proper rear air baffle, and an improper or misaligned limit and/or limit shield. Condemning the switch before airflow is proven is the classic misdiagnosis on this code.
Checks to run before you replace anything
- SAFETY: this is a gas appliance reporting overheating or flame rollout. Never bypass a limit or rollout switch to get heat, and never reset a tripped rollout switch until the cause is found — Bryant's caution requires correcting inadequate combustion-air supply or component failure first. Gas smell, scorch marks or soot at the burner compartment, or a CO alarm: furnace off, licensed technician (gas utility for a gas smell).
- Replace the filter — do not just look at it — and open every supply register and return grille. Bryant puts filter and duct restriction first because they are first in real life; a large share of 33s end here.
- Confirm the blower actually runs while 33 shows — Bryant's control runs it for 4 minutes or until remake to cool the exchanger. A furnace flashing 33 with a silent blower points at the motor, capacitor or wheel, not the filter.
- Time the event before you touch anything. A switch remaking inside 3 minutes keeps the story at 33; one still open past 3 minutes becomes lockout 13. Which you are looking at changes what you do next — and the timing is free evidence.
- Work out which switch opened, by behaviour: the main limit remakes by itself as the furnace cools; a rollout switch does not — it needs a manual reset (or a replaced fuse link). A 33 that never clears on cooling is the rollout branch until proven otherwise, and that branch is technician territory.
- Read the stored history before resetting anything (blower-door playback, or the Evolution Connex service screens). A lone 33 on the coldest night and a stack of 33s climbing toward 13 are different furnaces; the history tells them apart.
How to fix bryant error code 33?
- Restore airflow: new filter, all registers and returns open, and the duct restriction corrected at its source.
- Blower branch: tighten or refit a loose blower wheel, replace a defective blower motor or capacitor, and correct a wrong speed tap — technician work, verified by the blower running through the full 4-minute cooling run without the code returning.
- Vent branch: clear the restriction, correct improper vent sizing, and address termination placement where excessive wind is the documented driver — venting is combustion work, not carpentry.
- Firing branch: a technician sets the input rate / low-heat gas input adjustment to the rating plate and deals with a stuck high-heat gas-valve solenoid. Never adjust gas input yourself.
- Rollout branch: correct the inadequate combustion air supply (or failed component) FIRST, then — and only then — manually reset the rollout switch or replace the fuse link, per Bryant's service label instruction ('Reset switch or replace fuse link'). A rollout that trips a second time is a stop-and-diagnose event, not a reset routine.
- Switch branch, last: replace a limit or rollout switch, or repair its connections, only after airflow, blower and firing are proven — a technician confirms the temperature rise across the furnace sits inside the range on the rating plate before condemning the switch. On variable-speed models, also verify the rear air baffle and the limit/limit-shield alignment Bryant names.
The part that usually fails: Usually NO part — airflow is the fault (filter, duct restriction, blower); the limit switch itself is last
Bryant's check lists for 33 are airflow and blower lists, with 'defective switch or connections' at the end. The deciding measurement is temperature rise — supply-air minus return-air temperature — against the range on the rating plate: rise above the plate range condemns the airflow; rise inside it, with the limit still opening, finally condemns a switch.
How to reset bryant furnace error code 33?
Code 33 is not itself a lockout and has no reset button: the burners stay off, the blower runs its 4-minute (or until-remake) cooling period, and the code clears when the switch remakes as the furnace cools — 33 keeps flashing until the blower shuts off even when the switch remade quickly. Two Bryant-documented exceptions: the rollout switch never remakes on its own (manual reset, or replace the fuse link, only after its cause is corrected), and a switch still open after 3 minutes converts the event to lockout 13, with 13's 3-hour auto-reset. Power-cycling a 33 without fixing the airflow just schedules the next trip.
Bryant's lockouts run on documented timers, and they are not interchangeable. Limit lockout (13) and ignition lockout (14) auto-reset after 3 hours. Blower motor lockout (15, variable-speed boards) also auto-resets after 3 hours. Control circuitry lockout (45) auto-resets after 1 hour, and Bryant adds: reset power to clear the lockout — if 45 repeats, replace the control. Gas heating lockout (21) is the exception with NO auto-reset: Bryant's instruction is to turn off power and wait 5 minutes to retry. The pressure-switch behaviour under 31/32 (inducer shuts off for 15 minutes after the switch has been open 5 minutes, then retries) is a retry pause, not a lockout. Everything else on the Bryant chart is a condition code that clears when its condition clears: 33 ends when the limit or rollout switch remakes as the furnace cools (the rollout switch itself is manual-reset hardware — no timer resets it, and Bryant requires its cause to be corrected before it is reset), and 24 ends only when the 24-volt short is repaired and the fuse replaced. Interrupting power restarts a Bryant control, but on the older boards it also erases the stored fault history — read the history first, and never treat a cleared timer as a repaired furnace: an unfixed cause simply walks the control back into the same lockout.
Why does bryant furnace error code 33 keep coming back?
A 33 that returns after a filter change and open registers means the restriction is deeper or the blower is fading: a matted blower wheel, a clogged indoor coil, collapsing duct liner, or a capacitor losing strength week by week. A returning rollout trip is more serious — venting or combustion air is still wrong — and must not be managed by repeated manual resets. Each limit trip is a thermal cycle the exchanger did not need; a furnace tripping weekly is ageing its exchanger on every trip.
How to stop 33 coming back
- Dirty filter or restricted duct system: First on Bryant's check list for 33 on every label. A loaded filter, closed or blocked registers and returns, or an undersized or crushed duct run starves the heat exchanger of airflow, and the limit opens to protect it.
- Blower failure: defective motor or capacitor, loose blower wheel, wrong speed tap: Bryant lists the blower family together on the 340AAV label: defective blower motor or capacitor, a loose blower wheel slipping on its shaft, the blower set on an incorrect speed tap. If the air does not move, the limit finds out first.
- Furnace firing too hard: input rate set too high: Also on Bryant's lists (340AAV: 'input rate to furnace set too high'; 355MAV: 'improper low-heat gas input adjustment', 'stuck high-heat solenoid in gas valve'). A furnace making more heat than its rating — or stuck on high fire — overheats even with honest airflow. Firing-rate work is gas work: technician only.
Retrieving stored fault codes on Bryant furnaces
Every Bryant status code in these manuals is a two-digit number read off the status LED at the indicator in the blower door: the first digit is the number of SHORT flashes, the second digit the number of LONG flashes (33 = three short, three long). Three steady states frame the codes: LED continuously ON means the control has 24 VAC power; continuously OFF means check for 115 VAC at L1 and L2 and 24 VAC at SEC-1 and SEC-2; RAPID flashing means line-voltage polarity is reversed. Stored history is played back, not guessed — and the method is generation-specific. On the oldest labels (330JAV/393AAV), briefly remove and reconnect one main limit wire without removing power or the blower door; those boards erase stored codes when power is interrupted or 48 hours after each fault is cleared. The 340AAV red-LED boards and the variable-speed 355MAV erase stored codes automatically after 72 hours; the 355MAV recalls history by disconnecting the R lead (or the ABCD User Interface connector), resetting power and putting setup switch SW1-1 ON, and clears it by jumpering R, W/W1 and Y/Y2 simultaneously until code 11 flashes. The Evolution 987M changed the rule: its stored codes are NOT erased when 115- or 24-volt power is interrupted — the control stores up to the last 7 status codes in order of occurrence; with no thermostat signal present and all blower-off delays complete, set SW1-1 ON and the control flashes up to 7 codes, the 8th code always being 11, and a continuously lit amber LED afterwards confirms proper operation. On Evolution systems the Connex wall control adds its own reporting layer on top of the board: a Last 10 Events record and service screens — including Furnace Status, and, on compatible models, an Advanced Diagnostics view naming the most likely root causes of the most recent fault. The component test (setup switch SW1-6) runs the inducer, igniter and blower in sequence and reports back in codes (11, 25, 41 and 42 on the 355MAV; 11, 25, 35, 41 and 42 on the 987M). Whatever the generation, the service label printed inside your own Bryant's blower door is the chart of record for that furnace.
Other Bryant furnace error codes
| Code | Meaning | First fix |
|---|---|---|
| 11 | No previous code — not a fault: 11 is the end marker of the stored-history playback, showing no fault is stored (or none remains) | No repair needed. Bryant's label directs: run the system through a heating or cooling cycle to check it |
| 12 | Blower on after power up — normal operation, not a fault: the blower runs 90 seconds when the furnace is powered up during a call for heat (R–W closed), or the call ends during the blower on-delay | No repair needed. If 12 shows with no power event and no heat call, have the thermostat call and control checked |
| 13 | Limit circuit lockout — lockout occurs if the limit or flame rollout switch is open longer than 3 minutes, or (variable-speed Bryant wording) 10 successive limit trips occurred during high-heat. The control will auto-reset after 3 hours. Bryant's label cross-refers every 13 to code 33 for the diagnosis. | Fix code 33's cause — that is the whole of 13's repair, by Bryant's own cross-reference. Airflow first: filter, registers, returns, duct restriction corrected at the source. |
| 14 | Ignition lockout — the system failed to ignite gas and prove flame in 4 attempts (the trial plus code 34's three retries). The control auto-resets after 3 hours | Do not keep resetting it. Diagnose as code 34 (see the ignition codes guide); gas and flame-sense work is licensed-technician work |
| 15 | Blower motor lockout (variable-speed boards) — the blower failed to reach 250 RPM, or to communicate within 30 seconds of switch-on, in two successive heating cycles. Auto-resets after 3 hours | Technician work — code 41 twice in a row. The repair is the proven blower, wiring or control, not another reset |
| 21 | Gas heating lockout — the control has locked out of gas heating and will NOT auto-reset. Bryant: turn off power and wait 5 minutes to retry | Power off, wait 5 minutes, retry once only. A returning 21 is a control or gas-valve wiring fault — licensed-technician work |
| 22 | Abnormal flame-proving signal — flame is proved while the gas valve is de-energised. The inducer runs until the fault is cleared | Do not run the furnace. Technician test: shut the external manual gas valve — if 22 stops, the gas valve is replaced; if not, sensor or control |
| 23 | Pressure switch did not open — a switch contact is still made (closed) when a call for heat begins, before the inducer runs; the control flashes 23 until the switch opens, then the cycle can begin | Never bypass the switch. A technician clears or replaces the tubing and replaces a switch that stays made |
| 24 | Secondary voltage fuse is open — the fuse protecting the control's 24-volt (secondary) circuit has opened because there is a short circuit in the secondary-voltage wiring. On the Evolution 987M the fuse is an automotive-type 3-amp fuse located on the control, and Bryant states the control LED will display status code 24 when the fuse needs to be replaced. | Repair or replace the shorted wire run — thermostat cable, limit-circuit wiring, pressure-switch wiring, gas valve lead or accessory (humidifier) circuit, as the isolation proves; a humidifier solenoid or diode bridge drawing excessively is replaced. A wire that has chafed through once is replaced or properly re-insulated and re-routed, not taped against the same edge. |
| 25 | Model selection or setup error (variable-speed/Evolution boards) — the model plug (PL4) is missing or incorrect, or a setup switch is misplaced. If 25 flashes only 4 times on power-up, the control is defaulting to the model stored in memory and runs as if the plug were fitted | Technician work: fit the correct plug for the exact model (per the wiring diagram; read only on power-up) and return setup switches to OFF |
| 31 | Pressure switch did not close or reopened — on two-stage/variable-speed boards, the HIGH-heat switch (or its relay); single-stage boards print the same 31 for their one switch. Open over 5 minutes: the inducer shuts off 15 minutes before retry | Clear the outdoor vent/intake terminations first. Draft, switch and inducer diagnosis is technician work — never jumper the switch |
| 32 | Low-heat pressure switch did not close or reopened (two-stage/variable-speed boards; the label also covers the draft safeguard or aux-limit switch where used). Opens within 5 minutes after ignition: the next cycle is restricted to high-heat | Clear terminations and check the condensate trap/drain on condensing models; the rest is measured draft and switch diagnosis by a technician — never jumper it |
| 34 | Ignition proving failure — flame was not sensed during the trial-for-ignition period. The control repeats the sequence 3 more times before lockout 14; a flame signal lost in the blower on-delay brings the blower on for the off-delay | Confirm the gas valve and shut-off are on; sensor (cleaned with fine steel wool), igniter, pressure and ground checks are technician work — see the ignition guide |
| 41 | Blower motor fault (variable-speed boards) — the blower failed to reach 250 RPM, or to communicate within the time limits: 30 seconds after switch-on, 10 seconds in steady-state operation. In the component test, 41 means the blower failed the test | Technician work: prove wheel freedom, wiring and control before replacing motor or module. Two successive cycles of 41 escalate to lockout 15 |
See the full list on the Bryant Furnace error codes hub.
Codes 33 gets confused with
13 — Limit circuit lockout — lockout occurs if the limit or flame rollout switch is open longer than 3 minutes, or (variable-speed Bryant wording) 10 successive limit trips occurred during high-heat. The control will auto-reset after 3 hours. Bryant's label cross-refers every 13 to code 33 for the diagnosis. Code 13 is code 33 that did not clear in time — Bryant prints the relationship on every service label ('Refer to status code #33') because 13 has no separate cause list: it is the lockout the limit circuit escalates to.
24 — Secondary voltage fuse is open — the fuse protecting the control's 24-volt (secondary) circuit has opened because there is a short circuit in the secondary-voltage wiring. On the Evolution 987M the fuse is an automotive-type 3-amp fuse located on the control, and Bryant states the control LED will display status code 24 when the fuse needs to be replaced. Code 24 is the Bryant control protecting itself, and it starts with what 'secondary voltage' means: the transformer steps line voltage down to the 24 VAC that runs everything the furnace thinks with — thermostat circuit, limit circuit, pressure switches, gas valve, and accessories such as the humidifier terminal.
Frequently asked questions
What does code 33 mean on a Bryant furnace?
Limit circuit fault: a limit switch or the flame rollout switch is open. The control shuts the burners off and runs the blower for 4 minutes or until the switch remakes, whichever is longer. Bryant's check list starts with a dirty filter or restricted duct system, then the blower (motor, capacitor, loose wheel), venting, combustion air and firing rate — the switch itself last.
What is the difference between Bryant codes 33 and 13?
The same event at two stages. Code 33 is the active fault — the switch is open now. If it stays open longer than 3 minutes, the report changes to code 13, limit circuit lockout, and the control auto-resets after 3 hours. Fix 33's cause and 13 never happens; a furnace showing 13 is telling you the 33 condition persisted.
Why does the blower keep running while my Bryant shows code 33?
Because Bryant designed it that way: with a limit or rollout switch open, the control runs the blower for 4 minutes or until the switch remakes, whichever is longer, to carry stored heat out of the heat exchanger; the code keeps flashing until the blower shuts off even if the switch remade sooner. A silent blower during 33 is itself a clue — motor, capacitor or wheel.
My Bryant's rollout switch tripped. Can I just press the reset button?
The switch is manual-reset by design, but Bryant's caution sets the order: correct inadequate combustion air supply or component failure BEFORE resetting it — the service label pairs it with 'or replace fuse link'. A rollout trip means flame left the burner compartment; resetting into the same conditions invites the same trip, or worse. Treat a tripped rollout as a technician call, not a button.
Does code 33 mean my limit switch is bad?
Rarely — it is the last thing to conclude. Bryant's cause lists for 33 are dominated by airflow (filter, duct system), blower (motor, capacitor, wheel, speed tap), venting and firing-rate causes, with 'defective switch or connections' at the end. A technician proves the temperature rise is inside the rating-plate range before condemning the switch; replacing it into an overheating furnace gives the new switch the same job.
How to fix bryant error code 33?
Start here: Restore airflow: new filter, all registers and returns open, and the duct restriction corrected at its source. Blower branch: tighten or refit a loose blower wheel, replace a defective blower motor or capacitor, and correct a wrong speed tap — technician work, verified by the blower running through the full 4-minute cooling run without the code returning.
What does bryant furnace error code 33 mean?
Limit circuit fault — a limit switch or flame rollout switch in the limit circuit is open. The blower runs for 4 minutes or until the open switch remakes, whichever is longer; open longer than 3 minutes, the code changes to lockout 13; remade sooner, 33 keeps flashing until the blower shuts off. The rollout switch requires manual reset. Code 33 is Bryant's overheating-and-rollout report, with identical wording across the whole Bryant line — limit or flame rollout switch open, blower runs 4 minutes or until the switch remakes, 3 minutes to lockout 13 — printed on the single-stage 340AAV, 330JAV and 393AAV service labels, in the 577D control section, and in the variable-speed 355MAV guide.
How to reset bryant furnace error code 33?
Code 33 is not itself a lockout and has no reset button: the burners stay off, the blower runs its 4-minute (or until-remake) cooling period, and the code clears when the switch remakes as the furnace cools — 33 keeps flashing until the blower shuts off even when the switch remade quickly. Two Bryant-documented exceptions: the rollout switch never remakes on its own (manual reset, or replace the fuse link, only after its cause is corrected), and a switch still open after 3 minutes converts the event to lockout 13, with 13's 3-hour auto-reset. Power-cycling a 33 without fixing the airflow just schedules the next trip.
Why does bryant furnace error code 33 keep coming back?
A 33 that returns after a filter change and open registers means the restriction is deeper or the blower is fading: a matted blower wheel, a clogged indoor coil, collapsing duct liner, or a capacitor losing strength week by week. A returning rollout trip is more serious — venting or combustion air is still wrong — and must not be managed by repeated manual resets. Each limit trip is a thermal cycle the exchanger did not need; a furnace tripping weekly is ageing its exchanger on every trip.
Related guides
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