I have a Rheem furnace in my house. It recently stopped working.

It is the type where the pilot is not always on. Anyways, the ignition will kick in, and the pilot lights just fine. However, the spark ignition just keeps going and the main burners never turn on.

Unless I am mistaken, this furnace does not have a flame sensor, so I'm at a loss for what could be the problem. Any help is appreciated!

control unit gas valve lit pilot

  • Do you hear the main gas valve open (click, thunk, clank, etc.)? Does the furnace display any Error codes? What is the model number of the furnace?
    – Tester101
    Jan 11, 2016 at 3:25
  • @Tester101 no, the main gas valve never opens, as far as I can tell. The furnace doesn't have any display for error codes. Also, I unfortunately I don't know the model number. It was here when I got here and I don't see any indication on the furnace itself.
    – micahbf
    Jan 11, 2016 at 3:38
  • 1
    Your second picture shows, on the left side, parts of two labels plastered to the inside of the furnace housing. There is a good chance that there is some type of model number information on those labels.
    – Michael Karas
    Jan 11, 2016 at 4:18
  • It sounds to me like a relay on the electronics board for the furnace has gone bad. Particularly applicable if this furnace has some age on it. If this is the case the electronics board will require replacement. If you intend to replace the board yourself be aware that the range of prices you can find online will vary over a range of nearly 7 to 1. (I learned this the hard way after I paid a huge huge huge price to have a furnace man replace mine).
    – Michael Karas
    Jan 11, 2016 at 4:23

1 Answer 1


There is a thermocouple, the thing that is glowing red in the pilot light that tells the furnace the pilot lit. If that is bad it will continue to try to light the pilot. They are not real expensive but that would be the first thing to replace.

  • Thank you! Is this true even though this part is only hooked up to the "ignition" output of the controller, and not the "sensor" input?
    – micahbf
    Jan 11, 2016 at 21:57
  • Also would this fit the bill? supplyhouse.com/…
    – micahbf
    Jan 11, 2016 at 22:05

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