Why does my pilot light go out when I turn on the main burner?
Usually the pilot flame is too weak to survive the pressure drop when the main burner fires, or the thermopile — the sensor that powers the on/off valve under load — can't hold the valve open once the burner starts drawing gas. A dirty pilot orifice or a tired thermopile is the common culprit. It's a quick diagnostic for us.
Two flames sharing one gas supply
When you flip the switch or hit the remote, the main valve opens and the burner suddenly draws a lot of fuel. On a healthy system the pilot doesn't notice. But if the pilot orifice is partially clogged or the flame is already marginal, that surge of demand can momentarily starve the pilot enough to blow it out — and the safety valve closes right behind it. This is different from a pilot that dies at the knob; here it's the transition to the main burner that trips it.
Thermopile versus thermocouple
On many millivolt and electronic systems, a thermopile — a beefier cousin of the thermocouple, generating 300 to 750 millivolts — powers the whole on/off circuit. Under the load of energizing the main valve, a weak thermopile sags below the voltage needed to hold everything open, and the system drops out. Pair that with a pilot flame that isn't fully enveloping the thermopile, from spider webbing or a clogged orifice after the off-season, and you get exactly this symptom.
What we check
We inspect the pilot flame shape — it should wrap the sensors in a crisp blue cone — clean the pilot assembly, and test thermopile output both at rest and under load. A pile that reads fine cold but collapses when the burner calls is the classic bad actor. We also verify gas pressure at the valve, which matters especially on propane systems out in Fairview and Candler where a regulator or a near-empty tank can cause this. Those parts live inside the sealed gas control, so it's licensed work we handle — usually a single, affordable visit. Call (828) 545-0525.
Related questions
- Why does the pilot go out as soon as I release the control knob?
- What is a thermopile and how do I test it with a multimeter?
- My gas fireplace pilot is lit but the main burner won't come on — what's wrong?
- Why does my gas fireplace pilot light keep going out?
- Can spiders or insects clog a gas fireplace pilot?
- Why won't my gas fireplace turn on at all?
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