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Why does AC Blower Motor Fuse Blow after running on high speed for a few minutes?

Tiny
WIRENUT2TITE
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Started last summer. I can run ac/ heat blower fan on speed 1, 2, 3 all day long with no problems, but when I move to high speed it blows hvac fuse under driver seat. Sometimes it will run for 30 min before it blows and sometimes might be 5 min. I have replaced blower motor, blower motor resister hoping to resolve the issue but still blows fuse. I have tried a 30amp fuse (i know not recommended for 20amp cir)trying to figure if a dead short or thinking it could be my old blower motor drawing too many amps. Blows that too just as quick! I am an electrician by trade, and have put clamp meter on to check draw of motor. Even old motor was not over drawing. Any thoughts? Most internet searches I found deal with running on high speed only resistor issues but cant find any for my problem.
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Wednesday, May 30th, 2012 AT 9:54 PM

8 Replies

Tiny
CADIEMAN
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It sounds like the blower motor is drawing to many amps blowing the fuse. You need to replace the blower motor. Here is the blower motor location. Check out the diagrams (Below). Please let us know what you find.
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Wednesday, May 30th, 2012 AT 10:01 PM
Tiny
FIXITMR
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Definitely sounds like a short somewhere. Intermittent it would seem?
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Wednesday, May 30th, 2012 AT 10:03 PM
Tiny
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I tend to agree with Cadieman. It's probably excessive draw on the blower motor but it is possible for the Blower resister to short since is supplies both power and ground in one unit. I would measure the current draw of the motor when on high and see if it's close to limits or not.
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Wednesday, May 30th, 2012 AT 10:17 PM
Tiny
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Thanks for your input all of you! However, as I stated the blower motor & resister are both new! Both are good quality replacements. I tend to feel it is a short as well. Maybe a chaffed wire that shifts when I hit a bump or something. Anyone know what color wire I need to chase down for the high side. Orange perhaps? Could there be a problem with the blower fan speed controls? Is it possible it could have a ground and be internally shorted?
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Thursday, May 31st, 2012 AT 3:13 PM
Tiny
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High speed is orange
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Thursday, May 31st, 2012 AT 3:18 PM
Tiny
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A new part isnt a good part always. Unplug it, turn the a/c on and drive if the fuse doesnt blow your problem in the motor. Just take back and they will warr. It.
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Thursday, May 31st, 2012 AT 9:36 PM
Tiny
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Good suggestion cadieman I will try that tomorrow! Will let you know what happens.
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Friday, June 1st, 2012 AT 1:58 AM
Tiny
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If it still blows you can try the same test on the resister.
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Friday, June 1st, 2012 AT 2:03 AM

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