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Old 05-09-2020, 11:50 AM   #1
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Furnace only works one cycle and won't restart


Hello, hoping someone here can help me.

A few weeks ago I had a bird fly into my induction motor on my furnace. I have been working on it for a while now. Replaced circuit board, ind motor, and pressure switch. My wife just now admitted to me when it happened that she just couldn't wait for me to finish cooking breakfast and found some loose wires. She just started plugging them in. Hooked up a hot to the neutral terminal section and blew the circuit board. I've got a new circuit board. Hooked everything up, but the only way I can get anything to happen is to hook the humidifier directly to 120v. (don't even have a humidifier on this furnace) But the furnace now only runs for one cycle and the inducer motor won't shut off. Then when it goes to start the next cycle the fault light comes on for pressure switch stuck closed. (because the ind motor is running constantly.
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Old 05-09-2020, 12:24 PM   #2
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Re: Furnace only works one cycle and won't restart


Is the new board a new OEM replacement or something used off of eBay?
We need to verify correct wiring. Double check everything on the wiring schematic.
What are you hooking up to the humidifier terminals if you don’t have a humidifier?
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Old 05-09-2020, 12:27 PM   #3
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The board was bought used off ebay. Claims to have been taken off a working unit. Checked wiring. And replaced board as the wires were originally on the board in the first place.
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Old 05-09-2020, 01:15 PM   #4
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Re: Furnace only works one cycle and won't restart


You may have gotten a faulty board then.
eBay isn’t a suggested source for hvac parts.
Test with your meter and see if the board is at fault.
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Old 05-09-2020, 01:21 PM   #5
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Re: Furnace only works one cycle and won't restart


ebay is okay for parts if the seller is reputable and they're new closed box. lots of junk on there though.
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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
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Old 05-09-2020, 05:31 PM   #6
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What brand and model of furnace? Some furnaces if a limit is open the inducer will run all the time.
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Old 05-09-2020, 06:31 PM   #7
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This is an Amana furnace. Where might these limits be located. I've tested a few of them and they all checked out OK.
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Old 05-10-2020, 07:55 AM   #8
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Does the main blower run all the time too, or just the inducer motor?
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Old 05-10-2020, 08:43 AM   #9
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The main blower does not run all the time. Just the inducer motor. The main blower works as advertised.
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Old 05-10-2020, 10:08 AM   #10
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Re: Furnace only works one cycle and won't restart


Cool story, bro!

What is the blinking light trying to tell you?

What do you mean by "the only way I can get anything to happen is to hook the humidifier directly to 120v. (don't even have a humidifier on this furnace)"?

If you jumpered a 120V hot to the "HUM" terminal on the control board, then it's probably time to replace the control board again. The humidifier terminals on the control board are for 24V only.
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Old 05-10-2020, 11:11 AM   #11
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Can you send picture of board. You may have wired it wrong. Either the inducer is wired wrong or the board is bad.
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Old 05-10-2020, 05:55 PM   #12
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Re: Furnace only works one cycle and won't restart


Obviously the HUM terminals on your board are 120 vac. By backfeeding voltage to them, you are bypassing all control switches and powering up the inducer motor directly since it is always connected to the HUM terminals on a board with 120 vac HUM terminals. That's not a good idea although probably hasn't hurt anything... yet.

You need to find out why the board isn't getting power properly elsewhere. Use your meter and refer to the schematic and follow the line voltage input to locate the problem.

If it's giving codes, it must be powering some parts of the board. Verify that the 24 vac transformer is delivering full control voltage. It sounds like the board may be bad but we can't be sure without some testing with a volt meter.

A schematic or model number (or both) will help for us on this end to help you quicker.

Last edited by surferdude2; 05-10-2020 at 05:58 PM.
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Old 05-10-2020, 08:32 PM   #13
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Re: Furnace only works one cycle and won't restart


First off, what was that woman doing out of the kitchen!

I'm thinking since your YF shot 120 vac to who knows where, your thermostat may be fubar. You can unwire it at the furnace and use a jumper wire from the "R" terminal to the "W" (not heat pump) to see if the heat works. If it's a conventional system , then jumper "R" to the "Y"/"G" together to check and see if the cooling works.

If they all pan out OK, then you likely need a new thermostat.

Last edited by surferdude2; 05-10-2020 at 08:38 PM.
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