Symptom
Furnace repeated lockout
A furnace that locks out repeatedly is failing one of its own safety checks over and over: ignition, flame proving, draft proving or limits. Each lockout has a code; the code plus the fault history tells which check keeps failing.
Short answer
Read the status code and its minor digit exactly, and note whether the furnace runs for seconds, minutes or an hour before locking out. Repeated lockouts are the control doing its job; the underlying cause is found by testing the ignition, flame, draft or airflow path that the code names. Do not keep resetting, and if you smell gas, call FortisBC at 1-800-663-9911 or 911.
Have a code on the display?
What a lockout means
Furnace controls allow a fixed number of failed attempts, then stop trying until the fault clears or power cycles: that is a lockout. Carrier's 59TP6C, for example, documents lockout sub-codes for ignition, flame-loss events, pressure-switch events and blower RPM, and its label notes which codes auto-reset after hours.
A lockout is a symptom. The code names the check that failed; the cause is found by testing that path, which is why replacing parts because of the code alone is the wrong move.
Timing is diagnostic information
Locking out instantly says the sequence fails at start-up: draft proving, ignition or flame sensing. Locking out after minutes of running points at something that fails under heat or load: a limit opening, flame lost mid-cycle, a pressure switch dropping out, or an inducer or blower struggling. The stored fault history timestamps the events.
Weather and lockouts
Lockouts that appear only in cold snaps commonly trace to condensate freezing, ice at the vent termination, or a drain that backs up under heavy firing. These show up as pressure-switch, ignition or flame-loss codes depending on where the water interferes.
Related
- ServiceGas Furnace RepairFurnace repair in Greater Vancouver, diagnosed before parts are replaced
- ServiceEmergency Furnace RepairNo heat tonight? Call and speak to a person.
- ServiceFurnace DiagnosticsFind the actual fault before replacing parts: diagnosis by testing, not guessing
- SymptomFurnace not heating
- SymptomFurnace short cycling
- ComponentFurnace pressure switch
Questions people ask
How many times can I reset my furnace?
Follow the manufacturer's guidance: resetting once to confirm a code returns is reasonable; repeated resetting hides the fault, extends lockouts on some controls, and after ignition failures can let unburned gas accumulate. Stop resetting and call.
Why does my furnace lock out at the same time every day?
A consistent pattern usually tracks a consistent condition: a schedule on the thermostat, a draft change at a certain outdoor temperature, or a condensate path that fails after the furnace has run a certain length. The fault history confirms the pattern.
Is a lockout covered by warranty?
The failed part may be covered if the furnace is registered and the cause is not installation or maintenance related; labour is usually separate. The diagnosis must happen first to know which part failed and why.
Still no heat?
Call BC Wide with the brand, model number and anything on the display. Or
Request service online with this page attached.