Intermittent forced air furnace problem

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Old 01-02-10, 09:44 AM
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Intermittent forced air furnace problem

System is about 20 yrs old, a Payne Hi Eff. Only #'s I can find are on a tag on case are 395 CAV024055. Tstat is a Chromotherm III. Early morning when system light on tstat clicks on I can hear motor start. Then a couple seconds later it ignites and starts producing hot air.

Then before it gets to 70* fan shuts off yet system light stays on. If I turn tstat off manually then back on a couple seconds later will start back up. Sometimes it finishes heating other times it does the same thing. Only service it has had was a few years back a new igniter was installed.
 
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Old 01-02-10, 11:01 AM
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A likely source of a problem is a flame sensor that needs to be cleaned. On the side opposite of the hot surface ignitor you will see a rod that sticks up into the burner flames, with a wire going back to the circuit board.

Remove that with a 1/4" nut driver and clean it with a wire brush or some fine sandpaper. You don't need to dig into the metal, you are just cleaning invisible oxides that may be coating the surface of the sensor.

This is routine maintenance that ought to be done annually.
 
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Old 01-05-10, 03:50 PM
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Originally Posted by SeattlePioneer View Post
A likely source of a problem is a flame sensor that needs to be cleaned. On the side opposite of the hot surface ignitor you will see a rod that sticks up into the burner flames, with a wire going back to the circuit board.

Remove that with a 1/4" nut driver and clean it with a wire brush or some fine sandpaper. You don't need to dig into the metal, you are just cleaning invisible oxides that may be coating the surface of the sensor.

This is routine maintenance that ought to be done annually.
It's been 3 days and is working fine, that appears to be the problem. Thank you SeattlePioneer
 
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