# What makes a pilot light go out on a furnace?



## Guest

What would make a pilot light go out on a furnace? 3 times this winter I have had to relight the pilot light on our gas furnace, never happened before.


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## hatchet

I've had mine blow out in high winds.. really high winds is the only time. I imagine it gets blowing enough and it backdrafts through the exhaust pipe. This is pure speculation though.


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## Guest

There is also a thermal sensor which looks like a very small rod (maybe 1 inch in length) that the flame from the pilot contacts when it burns. The rod may need a cleaning or replacement. A small peice of sand paper may be all that is needed to clean it. Just shut the pilot down...let it cool and sand it down. Maybe a minute or two is all that it takes. If the sensor is dirty, this may cause your pilot to shut down.


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## Guest

*Standing pilot operation*



Mike F said:


> What would make a pilot light go out on a furnace? 3 times this winter I have had to relight the pilot light on our gas furnace, never happened before.



Ok here is how it works:

When the pilot flame hits the thermocouple it creates an electrical current that energizes a *small* solenoid inside the gas valve. This solenoid holds the pilot valve open and allows the pilot gas to flow. If the thermocouple gets too cool, the voltage will drop and the pilot valve will close cutting off gas to the pilot.

Weak, lazy, yellow pilot flames are not as hot as crisp, blue, noisy pilot flames. What makes them weak is the oxygen gets choked off. There are 4 air intake slots at the base of the pilot hood that allow oxygen in. They gradually clog up with dirt and make the pilot flame weak enough to be easily blown out. Keep you air slots clean and your pilot flame will stay strong.

Of course if the thermocouple is bad the pilot will go out.

If the pilot solenoid inside the valve goes bad the pilot flame will fail.

The main burners are lit by the pilot when the *large* solenoid inside the valve opens and lets gas flow. This is initiated by the thermostat calling for heat.


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## Bjd

Thermo couples are cheap, if you pay more than $10.00 you are getting screwed.
For the grief and aggravation with having to relite a poilet, you are much better off to just bite the bullet and replace the thing.

Bernie


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## Guest

*Alice/Universal card*

I was going to give you some suggestions, However it look as if they already gave you some very good answers. I hope you get your problem sloved and everything works good for you.


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## Guest

So, it looks like I should look into first doing some cleaning of air slots and sanding of that rod and then look into replacing some parts of the pilot light system.

Thanks guys.


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## Rod

My pilot light went out 7 times in the last 4 months because of high winds. I live in a new development and many other houses had the same problem. After several people complained to the builder (houses are still under the one year warranty) they have attempted to resolve the problem by lengthening the rooftop exhaust (B-vent I think they call it). They said that high winds swirling around the roof near the exhaust was causing the problem. The pipes were extended around 3-feet, many extending above the roof line. Anyway, that's what they did around here. Hopefully, it will work.


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## jedd

In response to sanding the rod on a thermocouple,c'mon.You need a tech in to check the millivolt readings on your thermocouple as well as a drop out time on your gas valve.Your problem is either a lazy flame ;a weak thermocouple;a weak gas valve solenoid or even a cracked heat x-changer.Downdraft hardly ever. Good luck.


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## CynicX

Rod said:


> My pilot light went out 7 times in the last 4 months because of high winds. I live in a new development and many other houses had the same problem. After several people complained to the builder (houses are still under the one year warranty) they have attempted to resolve the problem by lengthening the rooftop exhaust (B-vent I think they call it). They said that high winds swirling around the roof near the exhaust was causing the problem. The pipes were extended around 3-feet, many extending above the roof line. Anyway, that's what they did around here. Hopefully, it will work.


lol did they install old furnaces I cant believe you live in a new house with a furnace that uses a standing pilot...who makes the furnaces?, most name brand companies replaces standing pilot with electric spark ignition or electric spark pilot ignition in the late 80's.....


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