Pilot Ignitor Starts Up After Furnace Has Been Running
 

I have been called upon to assist a neighbor lady in fixing a problem she is having with her furnace. It is the same as my own, a 28 y/o Carrier (model #396GAW000075). It starts its cycle without any problems. After it has been running for about 10 minutes or so, the pilot ignitor starts to click/spark. The clicking gradually picks up speed and then there is a single louder click as if the pilot is trying to light (this is just a guess and I may be totally wrong as to what is happening at this point). This continues until the furnace turns off. I would greatly appreciate it if someone could diagnose this problem and how do I go about fixing it. I am trying to help my neighbor save a few dollars.

On a spark ignitor pilot after it lights the pilot flame goes from the pilot head to the flame rod and that should prove pilot flame so main gas can come on. Take the flame rod out and clean it with some fine sand paper, because it is not staying proven to the primary control. Make sure the pilot flame is a clean blue flame. It must be touching the pilot head and going around the flame rod.
Make sure you don't have a burner that is burning dirty and pushing the pilot flame away from the flame rod. Another thing that can cause the pilot flame to push away from the flame rod, is a cracked heat ex changer blowing air out on the pilot. Start by checking these things and let us know. Paul

Thank you for your assistance, Paul. Is there a site I can turn to that will have pictures or diagrams of what I need to do? I'm one of those guys that needs to see it before I do it.

Thanks again.

Gerry

They used a lot of different pilots over the years and i don't know of a site the goes into detail on cleaning pilots and flame rods. If you want to take pic. of your pilot assembly then i can see what you have. Usually you have a white wire under you pilot that connects to you flame rod that looks like a nail. You just clean it with some fine sand paper. Paul

Thanks Paul. I'll see what I can manage.

Sounds like Carrier bimetal pilot burner. The click you hear is the gas valve going from pick to hold. Probably worn out bimetal pilot switch