What it means
Limit circuit lockout: a limit or flame rollout switch was open longer than 3 minutes. Control auto-resets after 3 hours (see code 33).
⚠ Call a profurnace
How it shows: Status LED: 1 short flash(es) then 3 long flash(es) (code 13)
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
- 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 vent sizing and restrictions, blower wheel, blower motor/capacitor, switches and connections
- Technicianflame rollout switch requires manual reset only after the cause is found
⚠ 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 furnace locks out again after replacing the filter, or if a rollout switch has tripped.
Find a local HVAC pro →Other Carrier codes
21
Gas heating lockout. Control will NOT auto-reset.
22
Abnormal flame-proving signal: flame is proved while the gas valve is de-energized. Inducer runs until the fault is cleared.
14
Ignition lockout: system failed to ignite gas and prove flame in 4 attempts. Control auto-resets after 3 hours (see code 34).
23
Pressure switch did not open.
31
Low (LPS) or high (HPS) pressure switch did not close or reopened.
24
Secondary voltage (24 V) fuse is open.