I have a Tempstar natural gas furnace. It has electric element for
ignition of the pilot.

It was working fine all December. Now, it does not work as follows:
the draft fan starts and runs correctly, then a good looking pilot
light comes up. In less than one second, the pilot light turns off and
the main burner does not ignite.

I spent a while troubleshooting this issue. I cleaned the pilot sensor
with light emery cloth. It did not seem to help. It seems that if I
remove two screws holding the pilot light in place and pull it out of
the furnace, it does ignite and hold, and if I insert it back into the
furnace, the main gas ignites.

I put it back in and everything seems to work. I turn the furnace off,
then on, and the pilot stays and the burner lights. Then I went to
sleep and again woke up in a cold house.

Overall this behavior seems to be somehow "erratic". As in, things
seem to work, then after a while the pilot starts going away again.

Would there be some coherent explanation of this behavior.

On Wed, 04 Jan 2017 06:38:40 -0600, Ignoramus10081
wrote:

I have a Tempstar natural gas furnace. It has electric element for
ignition of the pilot.

It was working fine all December. Now, it does not work as follows:
the draft fan starts and runs correctly, then a good looking pilot
light comes up. In less than one second, the pilot light turns off and
the main burner does not ignite.

I spent a while troubleshooting this issue. I cleaned the pilot sensor
with light emery cloth. It did not seem to help. It seems that if I
remove two screws holding the pilot light in place and pull it out of
the furnace, it does ignite and hold, and if I insert it back into the
furnace, the main gas ignites.

I put it back in and everything seems to work. I turn the furnace off,
then on, and the pilot stays and the burner lights. Then I went to
sleep and again woke up in a cold house.

Overall this behavior seems to be somehow "erratic". As in, things
seem to work, then after a while the pilot starts going away again.

Would there be some coherent explanation of this behavior.

....Dirty wire connections / ground

.... Weak/low gas pressure?

.... Gas valve not staying open? Faulty?

On Wednesday, January 4, 2017 at 7:38:48 AM UTC-5, Ignoramus10081 wrote:
I have a Tempstar natural gas furnace. It has electric element for
ignition of the pilot.

It was working fine all December. Now, it does not work as follows:
the draft fan starts and runs correctly, then a good looking pilot
light comes up. In less than one second, the pilot light turns off and
the main burner does not ignite.

I don't know how your particular furnace works. Mine, there is
no pilot light, there is an igniter which just lights the main
burners. But given the behavior, if the flame detector is the
rod type, which is sounds like it is, that would be my first
suspect. They are basically just a metal rod, but I've heard
plenty of stories of strange behavior, where they would not
properly detect a flame and replacing it solved it. They are
also usually not that expensive and easy to replace.

Usually these furnaces have some LEDs that give an error code
that can be probative too.





I spent a while troubleshooting this issue. I cleaned the pilot sensor
with light emery cloth. It did not seem to help. It seems that if I
remove two screws holding the pilot light in place and pull it out of
the furnace, it does ignite and hold, and if I insert it back into the
furnace, the main gas ignites.

I put it back in and everything seems to work. I turn the furnace off,
then on, and the pilot stays and the burner lights. Then I went to
sleep and again woke up in a cold house.

Overall this behavior seems to be somehow "erratic". As in, things
seem to work, then after a while the pilot starts going away again.

Would there be some coherent explanation of this behavior.

On Wed, 4 Jan 2017 11:48:29 -0800 (PST)
trader_4 wrote:

I don't know how your particular furnace works.


Then you can't help the OP

On Wednesday, January 4, 2017 at 6:38:48 AM UTC-6, Ignoramus10081 wrote:
I have a Tempstar natural gas furnace. It has electric element for
ignition of the pilot.

It was working fine all December. Now, it does not work as follows:
the draft fan starts and runs correctly, then a good looking pilot
light comes up. In less than one second, the pilot light turns off and
the main burner does not ignite.

I spent a while troubleshooting this issue. I cleaned the pilot sensor
with light emery cloth. It did not seem to help. It seems that if I
remove two screws holding the pilot light in place and pull it out of
the furnace, it does ignite and hold, and if I insert it back into the
furnace, the main gas ignites.

I put it back in and everything seems to work. I turn the furnace off,
then on, and the pilot stays and the burner lights. Then I went to
sleep and again woke up in a cold house.

Overall this behavior seems to be somehow "erratic". As in, things
seem to work, then after a while the pilot starts going away again.

Would there be some coherent explanation of this behavior.

You could have a defective control board. I've seen cold solder joints on control boards in furnaces that didn't cause a problem until after the unit had been in operation for a while then a crack developed causing erratic operation. You might check into a new or remanufactured circuit board for your furnace. About the only thing you can do is to make sure every connection is good and tight where it connects to the control board. There are some other things that cause problems. Does you furnace have a diaphragm type prove air sensor to indicate that the draft inducer is running? It will be a pneumatic device with a red silicone rubber tube about a 1/4 inch in diameter connected to the draft inducer fan. The sensor can be a silver metal saucer shape the size of your fist or a black plastic short cylindrical shape. Sometimes the connection on the draft inducer fan can become clogged with rust or other debris. You can pull the silicone rubber tube off the the connection on the draft inducer and use a piece of wire or a drill bit that will fit the inside diameter of the hose connection and make sure it's clear. You can also blow into the the end of the silicone rubber hose connected to the sensor and hear a click. It takes very little air pressure to activate the sensor. Of course you can take some pictures of your furnace with the covers off and post them to a site like "http://tinypic.com/" and I could see what your furnace controls look like. ヽ(ヅ)ノ

[8~{} Uncle Furnace Monster