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.
Homeowner part this code names: furnace air filter.
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Bryant 33 on the 80% two-stage chart is the limit circuit fault while a limit, draft safeguard, flame rollout, or blocked-vent switch is open, or while the furnace is locked into high heat after two low-heat limit trips. The blower runs 4 minutes or until the switch remakes. Open longer than 3 minutes becomes lockout 13. The flame rollout switch needs a manual reset. A dirty filter is on this list. The 926TB install manual points its own lockout 13 at a status code 33, and that service-label figure is not copied here.
Same characters, different appliance: Bryant 33 on an AC / heat pump is a different fault. Bryant AC / heat pump 33.
Likely causes
- Dirty filter or restricted duct system
- Restricted vent or improper vent sizing
- Loose blower wheel
- Defective switch or connections
- Excessive wind
- Inadequate combustion air, if the flame rollout switch is open
Safe checks for 33
- Turn off power and check a dirty air filter. Open return and supply grilles that are blocked
- If a rollout switch has opened, leave the furnace off. The chart says the flame rollout switch requires a manual reset
- Techniciancheck the vent, the blower wheel, the switches, and combustion air before anyone resets a rollout switch
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
Call a licensed HVAC technician if 33 returns after a filter change, or if a rollout switch opened. The 926TB install manual also points lockout 13 at a code 33. That service-label figure is not the list on this page. This list is TG-GFB80-02.
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Parts & tools for this fix
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Furnace and AC air filter: guide
In this code: Dirty filter or restricted duct system
Furnace blower (circulator) motor: guide
In this code: Loose blower wheel
This one is for a technician to test or replace, so we only explain it and do not link to buy it.
High limit and rollout switches: guide
In this code: Inadequate combustion air, if the flame rollout switch is open
A safety device: we explain it but do not link to buy one.
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