Furnace Pilot Light and Gas Valve — How They Work Together
Published: July 23, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
The Pilot-Gas Valve Relationship
The pilot flame heats the thermocouple, which generates a small voltage that holds the gas valve pilot circuit open. If the pilot flame goes out, the thermocouple cools, voltage drops, and the gas valve closes — preventing unburned gas from flowing. This safety system is called the pilot safety circuit.
Common Failure Patterns
Pilot will not light: clogged pilot orifice, gas supply issue, or faulty ignitor. Pilot lights but goes out when you release the reset button: bad thermocouple (not generating enough voltage). Pilot stays lit but the main burner does not fire: the thermostat is not calling, the gas valve main solenoid is faulty, or the control board is not sending the signal.
Troubleshooting Steps
Step 1: Try relighting per the furnace instructions. Step 2: If the pilot lights but goes out, replace the thermocouple ($20-50, $150-250 installed). Step 3: If the pilot will not light, check that the gas supply valve is open. Step 4: If the pilot stays lit but the furnace does not heat, the issue is in the main gas valve or control circuit — call for professional service.