Technical heating guide
Flame Sensor Diagnostics
A flame sensor is part of a complete flame-proving circuit. Cleaning may help in some cases, but grounding, polarity, burner condition, flame quality, wiring, and control input also matter.
Safety: Do not open gas-fired equipment, alter gas settings, bypass safeties, or work inside electrical controls without the proper qualification. For a gas smell or CO alarm, leave and call the utility or 911 from outside.
Measure the signal
Flame rectification is commonly evaluated as a small DC microamp signal using the correct procedure and meter arrangement for the equipment.
Why cleaning is not always the fix
A weak signal can result from poor flame contact, burner contamination, grounding, wiring resistance, control issues, combustion, or the sensor itself.
Intermittent failures
Heat, vibration, moisture, condensate, loose connections, and changing combustion conditions can create intermittent flame-loss faults.
What to send before the visit
- Clear photo of the rating plate and model number
- Photo or exact wording of any error code
- Whether the issue affects space heating, hot water, or both
- When the problem started and whether a reset temporarily restores operation
- Your city and preferred service timing
Need service? Call 647-699-2474 or use the request form. Heating Experts will confirm the diagnostic visit and review repair pricing before approved work begins.
Technical service standards
Technical resources
Understand the system before approving the repair.
Use our knowledge hub for plain-language explanations of boiler lockouts, pressure problems, hydronic flow, combustion testing, condensate faults, OEM parts, and maintenance planning.