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Furnace Pilot Light Keeps Going Out
in Portland, ME
Older gas furnaces in Portland still use a small standing pilot flame to ignite the main burner. A lot of homes in the Rosemont and Woodfords neighborhoods still have these systems running. When the pilot won't stay lit, the furnace can't fire at all. Most of the time the fix is straightforward, but it needs to be done correctly because a pilot system that's bypassed or rigged is a gas safety hazard.
Quick Answer
A pilot light that keeps going out is almost always a bad thermocouple. The thermocouple is a small safety device that senses whether the pilot is burning. When it fails, it cuts the gas to the pilot even though everything else is fine. This is common in Portland homes with furnaces from the 1980s and early 1990s that still use standing pilots. It's an inexpensive fix. Call (207) 387-7691 to get it done before the next cold night.
Telltale Signs
Warning Signs to Watch For
- Pilot light is out when you open the furnace access panel
- Furnace won't start even though the thermostat is calling for heat
- Pilot lights when you hold the reset button but goes out when released
- Pilot flame is very small or yellow instead of blue
- Furnace hasn't fired since the first cold snap of the season
Root Causes
What Causes Furnace Pilot Light Keeps Going Out?
Failed Thermocouple
The thermocouple is a thin metal probe that sits in the pilot flame. Heat from the flame creates a small electrical signal that holds the gas valve open. After 15 or more years of continuous operation in a Portland heating season that runs from October through April, the probe wears out and can no longer generate enough signal to keep the valve open. The pilot lights, then dies within 30 to 60 seconds.
The Fix
Thermocouple Replacement
The old thermocouple is unscrewed from the gas valve and pilot bracket and replaced with a new one of the correct length. The pilot is relit and tested to confirm the valve holds open on its own.
Clogged Pilot Orifice
The pilot orifice is a tiny opening that controls how much gas reaches the pilot flame. Dust and spider webs collect in the orifice during the off-season, especially in Portland basement furnace rooms that sit idle from May through September. A partially blocked orifice makes the flame too small to fully heat the thermocouple, and the system shuts off the gas.
The Fix
Pilot Orifice Cleaning
The orifice is carefully cleaned with compressed air or a fine wire. The pilot flame height is checked against the manufacturer specification after cleaning to confirm full flow is restored.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Failed Thermocouple | Clogged Pilot Orifice |
|---|---|---|
| Pilot lights normally but goes out 30 to 60 seconds after releasing the button | ||
| Pilot flame is very small or yellow and barely visible | ||
| Furnace sat unused all summer and pilot won't light at the start of fall | ||
| Thermocouple probe shows corrosion or discoloration at the tip | ||
| Pilot flame goes out even on days when there's no draft in the basement |
Free Inspection
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