Furnace won't stay lit

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Old 03-25-05, 07:58 AM
Bgordon
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Furnace won't stay lit

My furnace will ignite and then shut off a few seconds later. A technician came out who said he wasn't familiar with Coleman gas furnaces but thought that the problem was caused by the automatic ignition system. The furnace is a Coleman THE 90. He wanted $300 for a new ignition system but I found the same part for $169. I don't mind buying the part if that's the problem but since he wasn't sure, I was wondering if anyone else had any ideas as to why the furnace shuts off imediately after igniting.
 
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Old 03-25-05, 09:30 AM
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Check the flame sensor

If you get ignition, and then the gas shuts off within seconds, odds are you have a problem with the flame sensor. I presume you have a wire sensor which extends into the flame.

If this sensor is dirty or corroded, it can be cleaned with steel wool or very fine sandpaper. Depending on the furnace model, it should be held in place with only one screw, or maybe two. Carefully remove it from its position and clean it, being careful not to "groove" or pit the surface.

Even if the flame sensor is bad, it is cheap compared to an ignition module.

Good luck.
 
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Old 03-25-05, 10:45 AM
Bgordon
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Furnace Won't stay lit

The techinician couldn't find the flame sensor and suggested that my model didn't have one. Is that possible?
 
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Old 03-25-05, 11:08 AM
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Flame Sensor

Not likely. There has to be some way for the control to know whether the
burners are lit. Otherwise, it would continue to pump gas and asphyxiate you. I'm not really up on Coleman, but there really has to be some way for your control to know if the burner is not lit.
 
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Old 03-25-05, 03:34 PM
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Technician?

Unless the servicer you delt with is a one person operation, call the office & ask them to send out someone with more knowledge.
 
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Old 03-25-05, 05:29 PM
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Good Advice

Good advice, Grady. There are a lot of techs out there who don't know much more than the homeowner....

I looked for some info on your unit, Bgordon, but not much is available online. On some furnaces, the hot surface ignitor and flame sensor are combined as one device. Do you have a hot surface ignitor? It could also be serving as the sensor. Wish I could be of more help, but Grady may have given you the best advice so far.
 
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Old 03-29-05, 08:48 AM
Bgordon
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Talking Furnace Problem

Thanks Harley, I didn't see you last post until today. The ingnitor is also the flame sensor. I decided to read the circuit diagram posted on the furnace which clearly showed that they were the same. The technician seemed to miss that part of the diagram when he looked at it. Anyway, I cleaned the ignitor with a piece of steel wool, hooked everything back up and the furnace is now working perfectly. I'm planning on sending a note to the heating company regarding the technician. I supposed he simply didn't know my furnace and wasn't trying to rip me off, but I find it a liitle strange that I was able to read the circuit diagram and he wasn't. I'm not an electrician.
This is a great message board!
 
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Old 03-29-05, 06:58 PM
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Congratulations!

Glad you got it going!

I know what you mean, with that technician problem. I've had to educate myself on heating/ac because I can't count on keeping a good tech either here at home, or on my two rental properties. I often get the same type tech you got.

I am a technician on large CNC woodworking equipment, used in the furniture industry, so schematics are not a mystery to me. I just had to get some direction on the control logic used in furnaces.

Hope you had a great Easter!
 
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