Lennox Boiler: Venting / flue fault
Air-pressure and flue faults on a Lennox boiler are a combustion-safety issue: a blocked, sagging or disconnected vent — or condensate in the sensing line — can spill flue gases, including carbon monoxide. The boiler locks out to keep you safe.
Air-pressure and flue faults on a Lennox boiler are a combustion-safety issue: a blocked, sagging or disconnected vent — or condensate in the sensing line — can spill flue gases, including carbon monoxide. The boiler locks out to keep you safe. On Lennox boilers, this is linked to 2 fault codes (Pressure Switch Fault, Blower Fault). Below are the likely causes, the safe checks you can make, and exactly what our licensed BC gas technicians do — because boiler repair in British Columbia is licensed gas work, not a DIY job.
This is a gas-safety fault. Diagnosing ignition, flame, gas or venting problems requires combustion analysis and gas-pressure testing that, by BC law, only a licensed gas technician may perform. Never bypass a safety lockout. Smell gas? Leave the building and call 911 or FortisBC at 1-800-663-9911 from outside.
What you might notice
- Lockout, often worse in wind, rain or cold snaps
- No heat or hot water
- Boiler tries to start, then faults during purge
- Boiler will not begin its ignition sequence
- Unusual fan noise or no fan sound at all
Safe checks you can make first
These are the only steps a homeowner should take. If they don’t resolve it, stop — the rest is licensed gas work.
- 1Check the outdoor vent terminal for snow, ice, leaves or a nest (from outside, safely)
- 2Note whether faults are worse in wind, rain or cold
- 3Never bypass an air-pressure switch or any venting safety
- 4Call a licensed technician to inspect the flue and combustion
Related Lennox fault codes
These Lennox codes are commonly behind “venting / flue fault”. Tap any code for its full meaning, causes and fix.
What our licensed technicians do
- Inspect intake and exhaust venting for blockage, sagging or disconnection
- Test the air-pressure switch and its sensing tubes for blockage or condensate
- Check the condensate trap and flue for water back-up
- Verify safe combustion and draft with analysis before return to service
- Test fan power, speed feedback (Hall sensor) and wiring
- Inspect the fan and venturi for debris, dust or seized bearings
Lennox venting / flue fault — FAQ
Why is my Lennox boiler showing a venting or air-pressure fault?
Air-pressure and flue faults on a Lennox boiler are a combustion-safety issue: a blocked, sagging or disconnected vent — or condensate in the sensing line — can spill flue gases, including carbon monoxide. The boiler locks out to keep you safe. The related Lennox fault codes are Pressure Switch Fault, Blower Fault. A licensed technician confirms the true root cause with the right instruments before any repair.
Is it safe to keep resetting my Lennox boiler when it shows "venting / flue fault"?
No. A single reset after a one-off event is fine, but "venting / flue fault" involves gas, ignition, flame or venting safety. Repeated resets without fixing the cause can be dangerous and can damage the boiler. If the fault returns, switch the boiler off and call GasBoilers.ca at 604-359-1081. If you ever smell gas, leave the building and call 911 or FortisBC at 1-800-663-9911 from outside.
Can you repair a Lennox boiler with this problem in Greater Vancouver?
Yes. Our Red Seal–certified, TSBC gas-licensed technicians diagnose and repair Lennox GWB8-IH gas-fired hot water boilers across Vancouver, Burnaby, Surrey, Richmond, the Tri-Cities and the rest of Greater Vancouver. Same-day appointments are often available — call 604-359-1081.
“Venting / flue fault” on other boiler brands
Lennox boiler venting / flue fault? We can help today.
Licensed, Red Seal–certified gas technicians across Greater Vancouver. Upfront pricing, same-day service available.