Gas furnace starts and stops every time we adjust the temp


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Old 01-01-11, 07:38 PM
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Gas furnace starts and stops every time we adjust the temp

I just finished my first home inspection and the biggest hangup is this heater. I need it to work to pass through FHA. The gas furnace will start up and then stop. Then we adjust the temp on the thermostat and it repeats again. I am going to suggest that the heater does not know that the flame is on, and then shuts down as a safety precaution??? I don't know, I'm just throwing that out. Anyway, here are three shots of 2 input wires. I hope the yellow wire with white ceramic looking tube one is the flame sensor and the red wire with the black boot is the ignitor. Any ideas what is going on? Thanks





 
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Old 01-01-11, 08:47 PM
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Possibly flame sensor/ignitor. But what is make and model? Could be vent/condensate issues too.

Mike NJ
 
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Old 01-01-11, 08:56 PM
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I'm pretty sure it is a Heil Quaker, model nugf080ag01. That is what the plate says. It says 1978 and 80,000.
 
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Old 01-02-11, 12:39 AM
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Ummmm.


Normally I would expect that furnace to have a Honeywell intermittent pilot ignition system.

But I don't see pilot tubing going to where I expect the pilot burner should be ---- where the red presumably high voltage spark wire is going.

Also Kevin, your description of what is happening when the thermostat is turned up is vague. You need to describe what happens carefully, completely, and in detail.
 
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Old 01-02-11, 10:54 AM
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To sum it up SeattlePioneer, we turned the newer looking digital thermostat to heat and raised the temp to like 70 degrees. The room temp said 56 degrees. The flames turned on along with the sound indicating that the furnace was burning. This continued for about 10 to 20 seconds and then stopped as though something was telling the system to stop. The little silver circle with the fan min and max on it in the furnace turned when the furnace came on and again when the furnace came off. There was no sign that the flame just died or anything like that. It was turned off deliberately. We had the door open on the furnace thereby taking the return air from the garage instead of through the 2 filters. The door safety switch was bypassed a long time ago. So something is telling the system to stop.

So I'm trying to find if it is:

thermostat?
flame sensor?
condenser on top of furnace?
blower not working?

I think this is the flame sensor/ ignitor
 
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Old 01-02-11, 12:04 PM
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Ahhh. The part you have is for a direct spark ignition system.


The high voltage is applied to one electrode and jumps to a second electrode which is grounded.

The third electrode is the flame sensor.


So no pilot burner. It lights the gas from the main burners directly.
 
 

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