Status code33Carrier
What it means
Limit circuit fault: a limit or flame rollout switch is open. Becomes lockout 13 if open longer than 3 minutes.
Basic checks firstfurnace
How it shows: Status LED: 3 short flash(es) then 3 long flash(es) (code 33)
§1Likely causes
- Dirty filter or restricted duct system
- Restricted vent or improper vent sizing
- Loose blower wheel
- Defective blower motor or capacitor
- Defective switch or connections
- Improper gas input adjustment
- Inadequate combustion air supply (flame rollout switch open)
- Excessive wind
§2Safe DIY steps
- Turn off power and check/replace a dirty air filter
- Make sure return and supply grilles are open and unobstructed
- Techniciancheck blower, venting, gas input and switches; flame rollout switch requires manual reset after the cause is corrected
Safety firstIf you smell gas, do not touch any electrical switch or use a phone in the building; leave immediately and call your gas supplier from outside. Turn off electrical power at the furnace switch or breaker before opening any panel, and never bypass or jumper a limit, rollout or pressure switch. Gas valve, burner, venting, wiring and control-board work should be done by a licensed HVAC technician.
§3When to call a pro
Call a licensed HVAC technician: if the code returns after a filter change, or if the rollout switch tripped.
Find a local HVAC pro →§4Other Carrier codes
13Carrier
Limit circuit lockout: a limit or flame rollout switch was open longer than 3 minutes. Control auto-resets after 3 hours (see code 33).
14CarrierIgnition lockout: system failed to ignite gas and prove flame in 4 attempts. Control auto-resets after 3 hours (see code 34).
21CarrierGas heating lockout. Control will NOT auto-reset.
22CarrierAbnormal flame-proving signal: flame is proved while the gas valve is de-energized. Inducer runs until the fault is cleared.
23CarrierPressure switch did not open.
31CarrierLow (LPS) or high (HPS) pressure switch did not close or reopened.