Whirlpool Nat Gas Furnace - 3 blinking red LEDs. Need help :)


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Old 02-18-13, 10:22 AM
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Question Whirlpool Nat Gas Furnace - 3 blinking red LEDs. Need help :)

Our furnace quit working. I'll try to describe in detail what the problem is. When turned on, the small blower (inducer blower?) starts to blow air, but after a few seconds of being on it starts to act almost like a switch is turning the motor off and back on a few times really fast. Sometimes the small blower will stay on long enough for the flame to ignite, but most of the time the furnace will turn off before the flame ignites, and I get 3 blinking red LEDs. The label on the cover says that this fault code indicates "Pressure switch, rollout switch, or aux limit switch open with inducer on"

This means the furnace is trying to ignite, but one of those switches is bad or exhaust (flue?) pipe is plugged, correct? The pressure switches are the ones with the rubber hoses attached. When the inducer is on, they should read closed. So I can use an ohm-meter as I turn on the furnace, and whatever switch reads ON is going to be the bad one? I am doubtful that the exhaust vent (flue?) is plugged because the furnace vents into a brick chimney in the center of the house (I'm guessing this was from using wood heat AGES ago)

Thank you for your helpp
Brandon



Thank you for looking
 
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Old 02-18-13, 11:07 AM
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Once the thermostat calls for heat....the draft inducer blower should start running and not shut down....especially turn on and off rapidly. That problem suggests a defective relay on the control board.

When the blower stops running prematurely is what is probably setting the 3 flash code.

Once the module detects an error.....at that point the inducer blower will be shut off and the system will be in lockout.

Can you post a model number for that furnace and maybe a part number listed on the control board.
 
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Old 02-18-13, 11:31 AM
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Furnace model# is WGFBT100B14-1B

I'm not sure on the control board but some noteable numbers on it were: 1170-83-1A , CPC-E 94V-0

I pulled a vacuum line, and of the two big round black honeywell switches (the pressure switches I believe) one of them when I suck or blow on the line makes a hissing noise, and the other one does not... Does this mean that the hissing switch has a bad diaphragm or is this normal?

Thank you so much!


EDIT: Wouldn't a defective inducer motor relay have trouble starting the motor from the beginning also?, as well as maintaining the speed? When I turn on the system the inducer starts right up and spins full speed it seems... it seems to start faltering after the furnace tries to ignite the flame... sometimes before it tries to ignite... (my conclusion is furnaces suck!! lol)
 
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Old 02-18-13, 11:59 AM
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Another note... the sheetmetal holding down the control board had some screws missing, I found them in the bottom of the furnace and replaced them. Also, the MAIN blower motor was only held on by one screw, I found and replaced it also. They were both in the bottom. I don't think that had anything to do with the problem, but while I was down there I tapped the relays on the board with the plastic end of my screwdriver, and turned on the heater. It is heating now just fine, so I can only assume that since all I did was rap on the relay, that the relay is failing as you say... If the pressure switch were still failed, the furnace wouldn't be running... so is it safe to say that it is probably just that relay??

Thank you so much for your help! It's now 75 degrees instead of 60...
 
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Old 02-18-13, 04:15 PM
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Good investigation work. Your problem was the missing screws on the control board. The boards rely on those grounds to work properly.

It could still possibly be the relay.....and if the problem comes back you'll know for sure.....but missing or poor grounds are major source of problems.
 
 

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