It started getting a little colder here so I fired up the furnace a week ago. It came on and was working. Then I noticed the house a little colder the last few days. I got up in the attic to check on the heater and the pilot light was out. No problem, re-light the pilot (took some doing to get it to re-light) and then the furnace kicked on and ran. Then later got a Heater Check message on the programmable T-stat. Looked and pilot light was out again. I did get it re-lit and then watched it cycle through. The pilot stays on until just before the blower shuts off. I can hear a switching noise and then it goes out. I double-checked the wires, made sure they were tight and they are in the same positions as last year. Any ideas what may be happening? Oh yeah, it is a Magic Chef Forced Air Furnace, mounted in the attic and the model # is G8A100DC48-10. Thanks for any help you can give. I am going to dig through to see if the last owner left me the manual.
Frank

Could very well be just the thermo-coupling. That is the tube that the pilot blows directley onto. It creates mili-volts to keep the gas valve open. Usally a very easy fix.

Could very well be just the thermo-coupling. That is the tube that the pilot blows directley onto. It creates mili-volts to keep the gas valve open. Usally a very easy fix.
To add to that, take it off and lightly sand it, so as to get a good read from the flame. Do not use any kind of joint compound on the thermal couple. It is an electrical connection. If that doesn't do it, it might be a faulty gas valve. Good luck.

Thanks guys. I will give that a shot. I also found the owners manuals.
Frank

That was it guys. I pulled the burner assembly and cleaned everything up, used some fine grit on the thermocouple and all is well. Thanks for the help!
Frank

Best run out and get yourself a new Thermocouple now because it will go out again.
You can't fix a weak Thermocouple by cleaning it.

A Thermocouple is not an electrical connection at the hot end.

Make sure a nice BLUE flame bathes the top 5/8" of the tip.

Best run out and get yourself a new Thermocouple now because it will go out again.
You can't fix a weak Thermocouple by cleaning it.

A Thermocouple is not an electrical connection at the hot end.

Make sure a nice BLUE flame bathes the top 5/8" of the tip.

Yep. In fact, buy two...they are cheap...your hot water tank probably uses one, too. I keep two or three hanging in the rafters in my basement right next to my furnace. They will no doubt break on a holiday or weekend in the middle of a snow storm and you would be SOL without a new one.

Best run out and get yourself a new Thermocouple now because it will go out again.
You can't fix a weak Thermocouple by cleaning it.

A Thermocouple is not an electrical connection at the hot end.

Make sure a nice BLUE flame bathes the top 5/8" of the tip.



Good advice. I will do that tomorrow. I am in Dallas so no real scare of a snow storm. :D We have ice once a year and it shuts this place down.
Frank

Best run out and get yourself a new Thermocouple now because it will go out again.
You can't fix a weak Thermocouple by cleaning it.

A Thermocouple is not an electrical connection at the hot end.

Make sure a nice BLUE flame bathes the top 5/8" of the tip.

You can fix it if it's dirty and that's the reason it's not working. I was trying to let him know not to use any joint compound on the threaded end, if and when he replaces it. It is an electrical connection and if he uses any, it will not get a good conection. He may not have known that and I was only trying to keep him from making that mistake, not prove to the rest of the world I know what a thermal couple does.

You can fix it if it's dirty and that's the reason it's not working. I was trying to let him know not to use any joint compound on the threaded end, if and when he replaces it. It is an electrical connection and if he uses any, it will not get a good conection. He may not have known that and I was only trying to keep him from making that mistake, not prove to the rest of the world I know what a thermal couple does.

Sorry, it is a electrical connection on the cold end.

I've been replacing thermocouples since I learned how to spell the word 43 years ago and I have never seen even one in all those years that cleaning would fix. (but then I wouldn't try that because I would be going back and working for free installing a new one in a day or two and I never cared for working without pay.)

I have seen plenty of dirty pilots that had a weak or yellow flame that didn't heat thermocouple enough though.

BUT you are correct, nothing should be put on the threads unless the pilot burner is pretty rusty, then a drop of oil maybe but I've never done that either.

Just my 2cents worth on the 5/8 blue pilot. A dirty and weak pilot can cause the same problem. as in when the burners shut down it pulles the pilot flame off. but it sounds like that got cleaned at the same time.

Glad you got heat!

I did notice that the pilot light was more of a yellow flame when I was having the issues. When I pulled the assembly their was quite a bit of "stuff" all over and some on top of the pilot assembly. After cleaning it all off the pilot was then the nice blue flame it should be. I think that was the main problem. I am still going to pick up an extra 1 or 2 thermocouples today anyways. Once again, thanks guys.