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  #1  
Old 08-16-2010, 03:25 PM
Chevy Guy Chevy Guy is offline
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Default Alternator gets hot with engine off

The alternator on my '06, 3.0L was getting hot with the engine shut off (eventually ran the battery down to zero). Since I suspected it was causing an annoying squeak anyway, I bought and installed a new alternator. Imagine my surprise when after I hooked it up I noticed it starting to get hot just like the old one. After I disconnected the battery, I checked a few of the wires with a multi-meter. I discovered that the heavy black/red wire bolted to the alternator was showing a full ground (even after disconnecting it from the unit). I noticed that I would only get a partial ground if I disconnected the 3-prong plug from the alternator.

Can anyone give me a clue as to what my problem might be?
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2006 Ranger Sport 5 spd 3.0L
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  #2  
Old 08-17-2010, 02:44 PM
Chevy Guy Chevy Guy is offline
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Default Re: Alternator gets hot with engine off

UPDATE!

I followed the troubleshooting steps in the factory repair manual and everything kept coming back to bad alternator (or at least a bad diode in the alternator). Finally, I sucked it up and took it back. I convinced the parts counter guy that the one he just sold me was defective right off the shelf and I went home with another new one... happy day, that fixed it!

This shouldn't have been such a painful thing to put right - I've never had a "dead on delivery" part before.
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  #3  
Old 08-17-2010, 07:28 PM
sgtsandman sgtsandman is offline
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Default Re: Alternator gets hot with engine off

Not uncommon actually. The previous owner of my truck had two bad ones in a row and they were both new, not rebuilds.

Glad you figured out the problem and got it fixed though.
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  #4  
Old 09-11-2010, 08:39 AM
Chevy Guy Chevy Guy is offline
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Default Re: Alternator gets hot with engine off

Unbelievable! I thought that I was done with this adventure.

Last week, I noticed that the alternator light would briefly come on with engine speeds above 3500 RPM. Since I rarely hit that speed and never drive at it (except maybe during a "spirited" acceleration up an on-ramp), I wasn't about to panic. Temporary high speed failures of an alternator indicate excessivly worn brushes - the brushes lift off the rotor at high speed because the fully extended brush springs lack the strength to hold them in place. I put it on my "get around to it" list and carried on.

Anyway, a couple days ago the inevitable happened - the light blinked on and stayed on... my 2nd replacement alternator had just koofered. After replacing 3 alternators in as many weeks, I was like a one man NASCAR pit crew - I had the old one out, drove it to NAPA for yet another exchange and the "new" one in and running all inside 40 minutes. I measured the output - at as high a speed as I would dare - and it appears to be OK (but then so did #2).

The good news is that all these alternators are not costing me anything but my time... but what a pain in the a$$ to have to keep swaping them out.

Third time lucky?
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  #5  
Old 09-11-2010, 09:24 AM
stephensimmons stephensimmons is offline
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Default Re: Alternator gets hot with engine off

Quote:
Originally Posted by Chevy Guy View Post
Unbelievable! I thought that I was done with this adventure.

Last week, I noticed that the alternator light would briefly come on with engine speeds above 3500 RPM. Since I rarely hit that speed and never drive at it (except maybe during a "spirited" acceleration up an on-ramp), I wasn't about to panic. Temporary high speed failures of an alternator indicate excessivly worn brushes - the brushes lift off the rotor at high speed because the fully extended brush springs lack the strength to hold them in place. I put it on my "get around to it" list and carried on.

Anyway, a couple days ago the inevitable happened - the light blinked on and stayed on... my 2nd replacement alternator had just koofered. After replacing 3 alternators in as many weeks, I was like a one man NASCAR pit crew - I had the old one out, drove it to NAPA for yet another exchange and the "new" one in and running all inside 40 minutes. I measured the output - at as high a speed as I would dare - and it appears to be OK (but then so did #2).

The good news is that all these alternators are not costing me anything but my time... but what a pain in the a$$ to have to keep swaping them out.

Third time lucky?
If it happens again get you a new battery also. Ive had a bad battery short an alternator out before
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