On the covered Carrier gas furnace, 33 means the limit, draft safeguard, flame rollout or blocked-vent switch is open, or the furnace is running in high-heat only because of 2 successive low-heat limit trips. The blower runs for 4 minutes or until the switch remakes, whichever is longer. If the switch stays open longer than 3 minutes the code becomes lockout 13. A flame rollout switch needs a manual reset. First, turn the thermostat down, replace a dirty filter, open all supply and return registers, and confirm the blower is running.
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0 of 2 completedWhat to do first
ReversibleTurn the thermostat down, replace a dirty filter, open all supply and return registers, and confirm the blower is running.
Correct only the documented fault domain
ReversibleThe most common owner-fixable cause is restricted airflow that overheats the limit. If 33 comes back with a clean filter and open registers, the guide sends a technician through the limit switch, the rollout switch, the blocked-vent switch, the draft safeguard, the vent (restriction, sizing, elbow baffle, wind) and the wiring harness. Never bypass these switches.
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What does 33 mean on a Carrier gas furnace?+
The limit, draft safeguard, flame rollout or blocked-vent switch is open, or the furnace is running in high-heat only because of 2 successive low-heat limit trips. The blower runs for 4 minutes or until the switch remakes, whichever is longer. If the switch stays open longer than 3 minutes the code becomes lockout 13. A flame rollout switch needs a manual reset.