Carrier furnace continues to spark while running

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Old 10-14-13, 09:03 PM
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Carrier furnace continues to spark while running

Hello, I have an older Carrier furnace model 58GS100150BA with a strange issue. The furnace seems to be running fine in that the thermostat calls for heat, the ignitor begins to spark and the pilot lights within a second or two but then the ignitor continues to spark. This continues for another 60 seconds or so and then the main burner fires and the furnace runs until the desired temp is reached. While the main burner is lit, the ignitor again continues to spark.

Any ideas what may be causing the problem? The pilot and main burner both light fine and stay lit for the duration of the heating cycle.

Thanks in advance,
-Chris
 
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Old 10-15-13, 04:51 PM
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Your furnace manual can be found at:

http://xpedio.carrier.com/idc/groups...t/58gs-3si.pdf

I would recommend that you print out a copy and keep it with your furnace if you don't have one.

Your furnace has a Carrier 3 wire pilot system that lights the furnace each time the thermostat call for heat.

Take the cover off the burner compartment. To the right of the burners there is a plstic box that operates the spark ignition. Is the box black or gray?

The pilot burner has a heat operated switch built into it. When cold, it energizes the spark to light the pilot. When the pilot burner heats it up enough, the SPDT switch should shut off power to the spark module and turn on the power to light the main burners.

It sounds like the switch may not be disconnecting power to the spark module as it should.
 
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Old 10-15-13, 06:54 PM
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Thanks for replying and for the manual, extremely helpful. The plastic box is black and has 2 sets of wires coming into the bottom.
 
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Old 10-16-13, 12:21 PM
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Connect a multimeter between terminal #5 on the electric gas valve and the C terminal. Observe the voltages when the thermostat calls for heat.

You should get 24 VAC when the thermostat calls for heat, and that should drop to zero when the main burners light.

If the voltage remains at 24 VAC while the main burners are lit, try tapping gently on the side of the pilot burner with the handle of a dinner knife. The pilot switch probably isn't disconnecting the voltage from the spark module as it should. If tapping on the pilot burner causes the voltage to drop to zero and the spark module to shut off, that's very likely what is happening.
 
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