No Furnace Blower

My daughter and son-in-law just took possession of a repo home that has a Goodman GMT090-3 furnace. We tried to get it fired up, but the blower doesn't work. I'm leary about just changing out the circuit board, but can't seem to measure any power across the motor. I also have continuity across the start capacitor. It is not the capacitor, but the wiring. Is this normal? The wiring diagram doesn't really help much so I don't know where to check the power across which leads. Any ideas would be much appreciated. We also don't have a manual at all so I have to wait until Goodman can send me something. Thanks.
Mike D
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Mike Dobony wrote:

The cap is not a "start" capacitor, but a "run" capacitor. It's always in the motor circuit and you are reading the winding resistances.
Does the thermostat have a "fan on" switch or something similar? See if the blower will run without gas flame.
Does the furnace attempt to light? Is there 24V to the board?
Symptoms??
You can go to Goodman site and look for info: http://www.goodmanmfg.com/Home/Products/tabid/53/Default.aspx Your model may no longer be listed, so pick one that looks close (multi-speed drive). Download a .pdf of the model specs.
But I think you'll be disappointed with the info they give out. Don't hold your breath waiting for the "manual" to arrive.
Helpful site: http://arnoldservice.com/Troubleshooting_Heating_Problems.htm
Jim
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Speedy Jim wrote:

Already did that.

It lights fine, but overheats because the blower doesn't run.

No idea. There is a 24V spade, but nothing hooked up to it. There is a red light that stays on.

Everything lights fine, just no blower.

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Mike Dobony wrote:

Quote: "> Does the thermostat have a "fan on" switch or something > similar? See if the blower will run without gas flame. >
Already did that. " --------------- OK. Did the blower run or not run??
---------------
Typically, the blower starts after a fixed time delay from light-off, which is built into the board.
If the board is getting 120V and 24V power, then the blower (circ) relay on the board is suspect. Check all the jumpers against the diagram too.
Jim
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Sounds like time to call a repair tech. Could be a bad motor, cap, or fan limit switch. Or some other wiring problem not otherwise specified.
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Christopher A. Young
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On Fri, 25 Jan 2008 02:07:33 -0500, "Stormin Mormon"

.........and once again Stormy the idiot shows us he hasnt the first clue in diagnostic ability. Three guesses and you still cant get it right as the OP posted it was the circuit board. What a totally stupid fool you are and yet you keep showing us everyday that you can get dumber and dumber with no problem at all. Bubba
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Bubba wrote:

When I went in to have the cap tested I also got a usable schematic that described the purpose of the various connections. The one on the door didn't have much useful info. Also working by flashlight alone, trying to push in the switch and check for power was a little awkward. I really do need to get some alligator clips for my meter. I suspected the board immediately, but without a good schematic it was rather difficult.
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AHEM! Why not just call the HVAC guy and let him make a proper diagnosis and repair?
s

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Mike Dobony wrote:

<SNIP>
.pdf of the exact model here:
http://www.hvacprotech.org/toc/Equipment%20Resi/Goodman/GPD075%20Service%20Manual.pdf
Jim
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On Thu, 24 Jan 2008 14:39:39 -0500, Speedy Jim

Thanks. Some fine day I'll need to replace my current old style furnace. Should I get a new furnace and there's a problem I can usually troubleshoot any equipment. But this manual let me know what to look for and will save a lot of digging around.
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Speedy Jim wrote:

http://www.hvacprotech.org/toc/Equipment%20Resi/Goodman/GPD075%20Service%20Manual.pdf

That helped. We ended up with a bad circuit board. The motor was good with straight power running across the leads (hooked up straight to the power lines), but had no power going to the leads from the board. Ended up being a bad relay, but since the relay is part of the board the whole board needed to be replaced. We still can't get the blower to run in the ON position, but it kicks in on AUTO, so we also have some bad wiring. Well, just one more wire to fix. We do have power to about half the house.
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Speedy Jim wrote:

http://www.hvacprotech.org/toc/Equipment%20Resi/Goodman/GPD075%20Service%20Manual.pdf
Thank you for posting that link. I've been looking for a manual for my Ruud.
--
Tony Sivori


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Good information. I'm not the O P, but the manual is chock full of useful info.
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check for 120v to the motor ??????????????????????????

doesn't work. I'm leary about just changing out the circuit board, but can't seem to measure any power across the motor. I also have Ccontinuity across the start capacitor. It is not the capacitor, but the pwiring. Is this normal? The wiring diagram doesn't really help much so I don't know where to check the power across which leads. Any ideas pwould be much appreciated. We also don't have a manual at all so I have to wait until Goodman can send me something. Thanks.pMike D
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Mike Dobony wrote:

You didn't say if you could read 120V anywhere in the furnace wiring. If not then there may be a switch mounted somewhere between the furnace and the breaker.
LdB
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L D'Bonnie wrote:

to fire up without electricity.
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On Thursday, January 24, 2008 12:24:36 PM UTC-5, Mike Dobony wrote:

Goodman manual, pdf found at: http://www.hvacpartsshop.com/Gmph075-4%20Series.Pdf
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Glad you found that for him. After all he's been without heat now for 5 years and the house must be very cold.....
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wrote:

Why? Is cold kind of like compound interest? The longer a house goes without heat the colder it gets?
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On Thursday, January 24, 2008 11:24:36 AM UTC-6, Mike Dobony wrote:

I found on 2 different brands of furnaces that through vibration (or defective solder) that the motor relays break loose and arcs until it oxidizes enough not to work. Re-solder is always an option apposed to hundred of $'s for the circuit board. If you don't have A/C there is usually an extra relay for it on the board. If you could remove it, you can replace the "heat" relay.
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