A. O. Smith Error 4 Flashes: CO Out of Limits
When connected to an A.O. Smith CO (carbon monoxide) detector accessory, the control flashes 4 times to indicate measured CO is out of safe limits, signaling a combustion or venting problem. We diagnose and repair it across Greater Vancouver — same-day and after-hours.
When connected to an A.O. Smith CO (carbon monoxide) detector accessory, the control flashes 4 times to indicate measured CO is out of safe limits, signaling a combustion or venting problem.
A. O. Smith fault codes can vary by model and series. Use this as a guide — the same code can have more than one cause. Our Technical Safety BC–licensed technicians read the code, confirm it against your unit's manual, and diagnose the true cause before any repair.
Likely causes of A. O. Smith error 4 Flashes
- Blocked or restricted vent / flue
- Poor combustion air supply
- Dirty burner causing incomplete combustion
- Vent/flue improperly installed or disconnected
- Recirculation of exhaust gases
What you can safely check
- If you suspect carbon monoxide, ventilate the area and ensure household CO alarms are working
- Turn the unit off at the thermostat/gas control
Beyond these checks, do not open the unit or touch gas/electrical parts — BC law requires a licensed gas fitter. Call us for a proper diagnosis.
Error 4 Flashes usually leaves you without heat or hot water and can indicate a safety-related fault. Don't keep resetting it — call for priority after-hours A. O. Smith repair.
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Parts often behind A. O. Smith error 4 Flashes
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A. O. Smith Error 4 Flashes Repair Across Metro Vancouver
Related A. O. Smith Venting & Combustion Codes
Frequently Asked Questions
Fix A. O. Smith Error 4 Flashes Today
Licensed A. O. Smith diagnosis and repair with genuine parts — same-day and after-hours across Greater Vancouver.
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