Blower Stays on and won't turn off (Carrier System)


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Old 01-05-13, 10:02 PM
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Blower Stays on and won't turn off (Carrier System)

I have a Carrier three wire pilot ignition system

I have done work on it before, changed the electrode.

Read more: http://www.doityourself.com/forum/ga...#ixzz2HATxlNvh

I know that all I need to do is change the fuse, I have almost gone thru about 4 in the past 3 weeks. For the last week I had no one (family) move the temp. I set it at 75, we usually turn it on in the morning for about 3 hours and at night for about the same amount of time. Now The system is connected to a thermostat, so the system does go on and off thru the course of the 3 hours (like normal). I just don't understand why I am flying thru so many number 3 fuses. Any Ideas?
 
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Old 01-05-13, 10:25 PM
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The only thing I know of that can cause that fuse to blow is a short in the control wiring especially to ground. That control wiring also includes thermostat wiring.
 
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Old 01-06-13, 02:22 PM
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The most common reason for a low voltage fuse to blow is the thermostat wire getting cut on some sheet metal ductwork, causing a short to ground, which is the ductwork.

So start by inspecting for that.

You can use a multimeter to look for zero ohms between R and C and R and W, either of which would indicate you have a short circuit which will likely blow the fuse again.
 
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Old 01-13-13, 10:09 PM
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Sorry I took so long, just wanted to be sure the problem was fixed, looks like it may have been a thin metal (kind of like a sticker) that was the only thing that was touching a wire. Other than that looks like the only thing that was touching. Once I saw that separated it, changed the fuse, have not had any problems since. Looks like that was it. Thank You for the help.
 
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Old 01-14-13, 12:34 PM
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Glad you got that repaired.

Just for our own education, can you describe in more detail where this piece of metal was connecting with the wire?

In particular, was this the theromostat wire and was it the sheet metal ductwork that cut into it, or something else?

Always interested in identifying what might be causing problems like this.


Incidentally, on older Carrier furnaces, the circuit boards had no fuses. When this kind of issue occurred, it usually burned out the transformer or some wiring before the low voltage current shut off.

Replacing the fuse might have been a nuisance, but it is a much better solution than these earlier issues!
 
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Old 01-15-13, 09:09 PM
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It was a metal like sticker that was almost under the electrode. The sticker was directly touching the electrode wire. I saw all other wires near the blower, touched around them and just made sure they where not touching anything. Since my last post no more fuse problems. I am still pretty sure that the sticker was the problem.
 
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Old 01-16-13, 01:16 PM
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Thanks for your reply --- I have never heard of that as a problem before, but there are a million things that can go wrong.


Good job of identifying the problem.
 
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Old 01-17-13, 09:52 PM
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Not anymore, it just blew the fuse again, and I am out of fuses now went through the whole pack. Starting gain from the beginning.
 
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Old 01-18-13, 01:11 PM
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Too bad.


Again I'd check out the thermostat wires and sheet metal. That's the most common cause of a blown fuse.


Also, you can use a multimeter set to ohms to check what is causing the short instead of blowing fuses.

For example, you can disconnect the thermostat wiring, connect one test lead to the furnace sheet metal ground and check the resistance to any and all thermostat leads. If you get one near zero ohms---- BINGO!

Chec k out each part of the low voltage system by these methods and you should be able to identify the problem.
 
 

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