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Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 19, 2009 08:27PM
We moved into our new house on Friday. That night the furnace (goodman gmv81155cxa) stopped working. I checked the control board fuse, and it was blown. I replaced it and a half hour later it blew again. I kept changing them until a tech came out. The tech came out and checked everything and said everything looked good. She couldnt decipher the code with the leds (too many blinks wasnt listed). I suggested that perhaps it was the thermostat. I sent her on her way and tried changing the tstat. The unit now went further than 45 minutes. Its now blowing a fuse every day and a half or so. I think its a short in the wiring from the furnace to the tstat. Anyone have any other ideas before I call in a better pro?
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Fred_Also
Date: August 19, 2009 09:05PM
If you think it is the tstat wire, why not hook it up on a short wire just on the outside of the furnace door? A piece of cat 5 would work for a temp tstat wire. Just keep track of the colors so it's wired the same.


Fred Also
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Re: Furnace keeps blowing fuses-any ideas?
Date: August 19, 2009 10:18PM
Only knowing a little about furnace controllers, my guess is there is a bad electrolytic capacitor somewhere that is shorting out part of the board in a certain operating mode.



in tha 510.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: JoeH
Date: August 19, 2009 10:34PM
Is the fuse that is blowing on the low voltage side or the high voltage side of the furnace control circuits? Low voltage, then a short in the thermostat circuit or another control could be blowing the fuse. Otherwise something is drawing too much current to close a relay or start a motor, or something else. Also check to see if a slow-blow fuse is supposed to be used, a fast acting fuse will blow under normal startup currents.



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Re: Furnace keeps blowing fuses-any ideas?
Posted by: davester
Date: August 19, 2009 10:48PM
A thermostat is nothing but a switch. Unless there's something very weird about your thermostat wiring, a short in the wiring between furnace and thermostat shouldn't do anything except turn the furnace on. It is almost certainly something within the furnace. Is this a new house/furnace or an old one? I'd hammer on the seller if it is an old one and I'd have the dealer/builder out there every day all day until it was fixed if it is new.




"In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion." (1987) -- Carl Sagan
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Dick Moore
Date: August 19, 2009 11:39PM
When this was happening at our church (it was the low-voltage fuse - an automotive ATO type), after several service calls, the tech finally found an intermittent short to ground in the wiring from the thermostat to the heat pump unit outdoors. Hasn't blown one since. Check the wiring in the air handler/furnace unit for any intermittent shorting to the frame during running vibration. Just shoving around on the wiring while it's running may help you find the problem. It's what our church service tech did...



What it is, man, a low-down and funky feelin'
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: freeradical
Date: August 19, 2009 11:58PM
Just replace the fuse with a penny.

- kidding!
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Racer X
Date: August 20, 2009 12:34AM
nah, it would need to be a nail of the right length.....

why are you running your furnace in August anyway? And wasn't it checked out as part of your home inspection you had done? You did pay, and have a home inspection done for YOU, right?



Edited 1 time(s). Last edit at 08/20/2009 12:36AM by Racer X.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 05:38AM
It was checked in the home inspection and it came up ok. We were here for three hours during the inspection, and it ran like a champ. Its about 3 years old, and we are trying to track down the selers through their realtor to see who installed the system.

As for the fuse, its the automotive type.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: cbelt3
Date: August 20, 2009 07:47AM
Stavs- most installers stick a label on the furnace with their contact information. If it's truly that young, you're probably under warranty.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 08:00AM
Thats the wierd thing...no sticker with the info. I looked all over the unit and found nothing. Its a nice system too. It has an electric air cleaner and humidifier as well. When its not blowing the fuse, it works like a champ-way better than the old house. Its a minor inconvenience, With the new thermostat it blows every day and a half. With the old one, it was 35-45 minutes.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: JoeH
Date: August 20, 2009 09:49AM
"As for the fuse, its the automotive type."

That means almost nothing by itself, there are so many types of automotive fuses. Some types even come with designs meant to be used in standard high voltage AC circuits, and others meant for low voltage AC or DC circuits.



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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 11:48AM
Quote
JoeH
"As for the fuse, its the automotive type."

That means almost nothing by itself, there are so many types of automotive fuses. Some types even come with designs meant to be used in standard high voltage AC circuits, and others meant for low voltage AC or DC circuits.

Its the bussman (i think thats what its called).
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: JoeH
Date: August 20, 2009 12:20PM
Bussmann is a manufacturer of fuses, all types. If you mean the glass tube type with metal end caps, those are used in both automotive 12 and 24 V circuits and 110 electrical equipment. They also come in both fast and slow blow varieties, and speeds in between. So the replacement has to match on size, voltage, amps, and speed rating.



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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 12:25PM
Its the blade type.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Racer X
Date: August 20, 2009 03:32PM
those are ATO or mini ATO. Whats the amperage rating?
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: JoeH
Date: August 20, 2009 04:47PM
ATC or ATM fuses are all fast acting, so just a slight over-current will blow them. Something in the controller is drawing too much power. Max voltage rating is 32 V, so it is on the low voltage side. Just need to find what is drawing too much. Is the thermostat electronic and powered from the furnace controller, or just a thermostatic switch? Another route is that they also make mini circuit breakers that will plug in place of an ATC or ATM fuse. Issue would be whether one was available in the correct voltage an amperage needed.







Edited 1 time(s). Last edit at 08/20/2009 04:47PM by JoeH.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 05:10PM
Tstat doesnt get power from the furnace, its battery operated (ran into tthat issue before).

My new HVAC guy came out today and is swapping the board first. Its under warranty, so he's going to try that. If its not the board, then its the wiring. For the mean time, I'll continue to replace fuses every day until the new board arrives on Monday. Wish I called this guy first.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: sunfalcon
Date: August 20, 2009 05:55PM
My fuse was blowing a lot and we had to have the blower motor replaced. No more blowing fuses.
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Re: Furnace keeps blowing fuses-any ideas?
Posted by: Stavs
Date: August 20, 2009 07:28PM
Quote
sunfalcon
My fuse was blowing a lot and we had to have the blower motor replaced. No more blowing fuses.

Well, luckily everything is covered under the warranty for a couple more years. If it does end up being that, I'm covered thankfully!
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