Coleman furnace Help!!

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  #1  
Old 10-13-08, 06:36 AM
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Coleman furnace Help!!

Hi,
I have a Coleman furnace it clicks on but does not ignight. Sometimes it does light and then works fine. It started doing this 2 years ago and last year it was worse. This year it is happening again. It is an electronic ignighter. It glows but when it does not light it go off. Then later it trys again.
Please help!!
jim
 
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  #2  
Old 10-18-08, 05:07 PM
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Location: Ontario, Canada
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Could use model etc., but am guessing that thermocouple needs cleaning for starters. If it can be disconnected at gas valve end, clean end up with steel wool or fine sandpaper, and try poking and twisting a piece of steel wool down in the valve where it came out, to clean mating surface. Blow out with compressed air after, or a straw. To put it quite simply, the heat from the ignitor is sensed through the tip of the thermocouple, and the signal is sent back to the gas valve, telling it that it's time to send gas for burner. Quite often that signal gets interrupted by dirt/corrosion at the mating surfaces where the end of the thermocouple (little probe like thing near the ignitor) goes into the gas valve. It's about a 10-15 min. job that can eliminate a lot of headaches. Let me know how it goes
 
  #3  
Old 10-18-08, 06:18 PM
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Question

It sounds like you have a glow coil that lights the burner(s) directly. The reasons the glow can dim down before the fire appears is either the glow coil is burning out and is a hair weak to ignite the gas, or the ignition control module is bad, or the gas is not coming out, or the gas is not coming out of the burner close enough to the glow coil, due to a blockage in the burner, from say rust scale.

If this were me, the very first thing I would do is to take a volt-ohm meter and test between the two wires of the glow coil to see if the "ohms" reading was about 75 or less. I have seen same brand/style coils vary by about 50 ohms, yet still fire off.

Then I'd move on from there. You really need someone capable, that is handy with a meter. It does not take a furnace man at this stage. Just someone capable of making that simple ohms test. Anyone who knows electricity and has a meter should know what to do. And I provided a top number. Although I think that sometimes they can still fire at 95. But I have seen the same identical glow coil give a reading of 27 ohms. (The lower, the better, without splitting hairs on technicalities).
 
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