Fedders F80A- White-Rogers integrated fan control

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Old 11-12-11, 05:37 AM
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Smile Fedders F80A- White-Rogers integrated fan control

Purchased and installed the Fedders F80A 4 ton last Summer. This model has a White-Rogers integrated fan control. Woke up to a cold house this morning. Furnace fan will kick on when set to "On" but will kick off on "Auto" setting with no heat.
Reset switch at furnace and furnace will run, fan will cycle, flames will kick on for about 10 seconds and shut back off. The furnace will cycle like this about 5 times in a row (kick on, 10 seconds, kick back off) and then shuts off completely. Fault red light on control panel blinks off and on slowly.
Checked filter, cleaned limit switch, and checked ground. Manual is vague on default code.

Any suggestions?
 
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Old 11-12-11, 08:30 AM
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You probably have a flame sensor in the furnace which is supposed to verify that the main burners have lit. If they don't light within 3-5 seconds, the furnace shuts off and goes through the ignition process again --- eventually shutting down for an extended period of time after several cycles.

Ten seconds would generally be too long for that if things are working properly.

It's worth a try, though. The flame sensor can get coated with invisible o9xides that prevent the flames from touvhing the metal of the flame sensor. It can be cleaned by brush the flame sensor with a wire brush or fine sandpaper --- you don't need to carve away the metal of the flame sensor.

The flame sensor is usually on the opposite side of the furnace from the hot surface ignitor. It's a thin rod sticking up into the burner flame area with a single wire coming out the bottom and going to the circuit board.

Give cleaning it a try. It's easy, costs nothing and should be cleaned annually in any case as ordinary maintenance.
 
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Old 11-17-11, 10:26 AM
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Fedders F80A-Flame Sensor Issue

SeattlePioneer

Thanks for your help!

Husband replaced several sensors this past weekend, he refused to believe it was the flame sensor so I let him have at it. House was an uncomfortable 60 degrees last night with the furnace still not staying on.

So, when he went to work today, I pulled out and cleaned the flame sensor. The sensor was covered in white residue. I gave it a few lashes with some sandpaper, just enough to knock off the debris, put it back into place and kicked on the furnace again. The furnace started up and stayed lit. I bumped up the temperature to 70 degrees and it stayed on with no more issues. The house is up to a nice comfortable temperature again.

Husband is eating crow for dinner and sleeping in the dog house tonight!

Thanks again!
 
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Old 11-17-11, 03:28 PM
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Don't beat the poor guy up. I'n sure he was doing the best he could. People tend to get highly motivated when the temperature starts to drop.

But this illustrates that guessing and supposing are not adequate diagnostic methods. That's somethin a LOT of people posting on this board need to learn.

The first key to diagnosing problems is to be a good observer of the sequence of events which have to heppen for the furnace to produce heat. You did a reasonable job of posting what had happened.

Then you need to be able to analyze the likely reason why the ignition process may have stopped and what can be done to test or repair for that problem. That's what my post contributed.

Lastly you need someone capable and willing to follow those directions to perform further tests or repairs --- and you did well on that.

So my suggestion is that you take a measure of pride in what you accomplished. What you did deserves commendation.

What your husband did was the best he could do, and about what most people would accomplish left to themselves. Without a little stubborness in his soul, he, and you too, probably wouldn't have gotten started.

I recommend cleaning the flame sensor annually as part of regular maintenance in order to avoid this kind of problem in the future.
 
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