Carrier furnace problem?
 

I just installed a used Carrier 58SS100 furnace, 1983 model and it is driving me nuts!!!! I am not an HVAC person but I can usually get things working. Not this!
I had the limit switch checked, spark sensor checked, new thermostat and I've checked all the conections I could find. When the thermostat is turned up, the exhaust gas fan kicks on, the pilot lights, and then the burners kick on, then the blower comes on. Great! It runs for about 20 or so seconds, at that time the burners kick off, but all the fans continue to run and the pilot stays lit. After 15 or 20 seconds of the burners being off, they come back on. The burners just continue to go on and off about every 20 seconds or so. I can't find a flame sensor anywhere. What is the deal? Help!!!!!! Theo in Louisville

Thanks for the reply. Exactly what would that look like and about how many wires? Thanks Theo

You mentioned the limit was "checked". Sometimes the hihgh limit can be installed backwards or if it is slightly bent it can come too close or touch the heat exchanger and cause improper operation.

Can you post a picture of the pilot assembly? Does it have three wires going to it? It sounds as if the unit isn't sensing pilot. It could be a damaged/shorted wire or maybe the pilot assembly if it's the one I think that unit has.

First off I want to thank you guys for attempting to help me!!! I do not see a nine pin connector black box. The only thing I see on the right side wall is a round black "spark ignitor". It has one red wire going to the spark thing that gets red hot, and it also has a double green wire and a double blue going to its two connectors. The pilot assembly does have three wires going to a silver box on the left side of the pilot. The three wires are green white and yellow. The limit switch that I had checked is a "180 limit switch" according to the man at the parts store. I have removed it from the heat exchanger while the furnace is running and that didn't effect anything. Surely I can't have the thermostat hooked up wrong can I? Any more help at all will be appreciated more than you can imagine.
Thanks Theo

Remove the pilot assembly that has the three wires going to it. The sensor is a small metal post that the spark goes to, you can try cleaning it or better yet replace the whole piece.

In other words I will not be doing anything to the silver box with the three wires? I took off the little dude that looks like a white insulator with a small bent metal piece coming out of it. This metal piece gets redhot when the furnace/pilot is on. If that is the piece, the man at the parts shop said that was the spark sensor and he said it is good. He kept telling me that there has to be a flame sensor going into the heat exchanger. If there is I sure can't find it. Theo

There is never a flame sensor in the heat exchanger. There are limits controls in the heat exchanger. On the pilot assembly there is the sparktrode which is the part I think you are talking about. There should also be a second similar looking piece that gets heated by the pilot and that is whaty passes current to the controls to open the main gas valve.

I'll go look at it right now.
Thanks Theo

BigMike-I took that whole assy off. Other than the part that the pilot gas goes into, there is that one little nail like job that gets red hot and then there is the chrome/stainless steel box about 1 and a half inches long and 1/2" wide by about 3/8" thick. It has the three wires, green, white, and yellow going to it. I looks like it has a round stainless "button with a white insulator looking top on it. Then, out under where the pilot is there is a piece of steel that looks like it goes back and fastens to that button. The steel flat piece looks kinda carroded from the pilot flame above it. Is the flat piece what "sees" the flame and do I clean it or what? Thanks theo

Change it out, it sounds pretty worn.

I will get one tomorrow. Thanks Theo-I'll let you know how I do. No matter what, I really appreciate the help!!!!!! If you ever need to know anything about a wrecked car email me. Theo

No problem.