# Hot surface ignitors



## Rich Koster (Apr 18, 2009)

Can a hot surface ignitor on a gas furnace be glowing, but not be hot enough to ignite the gas? I tried adjusting the regulator valve (had to do this in the past due to yellow flame), but no success. This unit is 3 years old.


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## LawrenceU (Apr 18, 2009)

Have you checked your flame sensor? If it is bad the igniter can glow all it wants, but the valve will not open.


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## Rich Koster (Apr 18, 2009)

LawrenceU said:


> Have you checked your flame sensor? If it is bad the igniter can glow all it wants, but the valve will not open.



I can hear the gas valve opening (and smell it if I check the exhaust). Through the sight glass I can see the glow, but no flame ever occurs along the burners. The ignitor turns off about 3 seconds after the gas valve opens and times out after 3 attempts to light (goes into lockout mode).There are led monitors on the control module and the flame sensor stays off also, confirming there is no combustion. I am guessing that even if the regulator was off adjustment, some sort of flame would appear, even if it was low or high and yellow. If I put my hand across the intake I can feel air going in, so I know the intake damper is working too.


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## Croghanite (Apr 18, 2009)

Rich Koster said:


> Can a hot surface ignitor on a gas furnace be glowing, but not be hot enough to ignite the gas? I tried adjusting the regulator valve (had to do this in the past due to yellow flame), but no success. This unit is 3 years old.



This may help.


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## LawrenceU (Apr 18, 2009)

Rich I've had a similar thing happen twice. Once on a burner in oven, the other time on our forced air heater. With the oven it was the valve. It was not opening properly. Gas would be released, but not enough to bring the mixture to ignition percentages. If you are getting a strong flow through the intake damper that means the combustion chamber is breathing. That is good. The orifice where gas flows onto the HSI may be sooted. You can have gas flowing through the burners and up the flue but never reaching the ignitor. This is fairly common, especially if you have had low flame issues in the past. 

On the heater it was the HSI not being hot enough. It was glowing, but it was about to go out. If you have ever touched the thing with your fingers that cause problems. This is really rare from what I've been told.

Do you have a multimeter?


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## Rich Koster (Apr 18, 2009)

Yes

-----Added 4/18/2009 at 11:17:13 EST-----

I think I'm going to order a HSI and put it in. If it doesn't fix the problem, I'll have a spare for when it does quit. Thanks to all for the input. When I get the new one, I'll compare the resistance reading and see how far apart they are.


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