Find my flame sensor

Old 01-20-13, 01:40 PM
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Find my flame sensor

Name:  furnace1.jpg
Views: 8006
Size:  40.2 KBI am trying to locate my flame sensor on my gas furnace...
Can someone tell me where it is... I have attached a file of my furnace..

Old 01-20-13, 02:00 PM
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Your furnace doesn't have the flame sensor most modern furnaces come with but neither did the OP's.

Center burner. You can trace the 1/4 inch aluminum tubing from the gas valve to it.
Your intermittant pilot module is the small rectangular grey box on the bottom of your pic.

Is you furnace having a problem?
Old 01-20-13, 02:43 PM
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Houston is correct.

You probably assumed that the rod in the pilot flame with the high voltage wire going to it is the flame sensor, but it's not. That rod functions as an electrode to help create a spark to light the pilot burner.

The high voltage electrode is also used to apply an AC voltage to the pilot flame when the pilot burner is lit and the spark is off. The pilot flame then rectifies that AC voltage which flows across the pilot flame to chassis ground and then from the furnace sheet metal to the ignition control module via the ground connection on the ignition module.

So the grounded metal cage around the pilot burner is actually the "flame sensor."

I always thought that was a pretty elegant method.
Old 01-20-13, 02:43 PM
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I have moved this to its own thread. You can remove the spark electrode/pilot assembly and clean it as it does act as the flame sensor.

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