alternator hot, engine off

2006 Ranger, 3.0L
The alternator 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 (engine off). 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 also noticed that I would only get a partial ground if I disconnected the 3-prong plug from the alternator.
Mostly just to see what would happen, I reconnected everything and fired the truck up. It sounded great and there were no indications of a problem from the vast array of idiot lights (or light). However, when I touched the casing of the alternator after 30 seconds of running, I almost left some skin behind it was so hot. I immediatly shut it down and disconnected and removed the battery. I'm starting to suspect that I just replaced an old bad alternator with a new bad alternator.
Any thoughts?
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My van runs fine sometimes and other it is grabby and seems the brakes catching. I have had it in and out of numerous repair shops to no avail. Sometimes it runs perfectly.==then is will catch and one wonders if he is going to arrive at destination. I have had adjustments-pads, caipers and I don't knw what all to attempt to fix it.
Help is you can.
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On 16/08/2010 8:46 PM, Wes wrote:

UPDATE.
So I gave in to the inevitable and took the suspect replacement alternator back and and picked up another one. Yup, that was the problem. Who'da thought that the one right off the shelf would have the exact same problem as the original.
Oh well, at least it's all fixed now.
On an interesting side note, before I gave up on the first replacement, I ran through a few troubleshooting tests. As such, I had re-connected the battery and started the engine for the operating portion of the tests. When I saw trouble lights indicating problems with the charging circuit, ECM and even the ABS system, I don't have to tell you that I got a sick feeling in my gut (it was right about then that I shut it all down and yanked the alternator again). Fortunately, everything was back to A-OK with the installation of the new (new) alternator.
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What was the brand of rebuilt you got? Just curious, I suspect most of them are only as good as the one year warranty they come with.
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On 22/08/2010 11:26 AM, Dick Cheney wrote:

I got them both from NAPA. Ironically, the first one (the dead on arrival one) was their "premium", life-time warranty re-man. I don't recall a particular brand name on it - a few Asian symbols. When I took it back, they didn't have any premium types in stock, so I took their "lesser", 3-year warranty re-man and a refund in the price difference. This second one - the one that worked - was actually an OEM Motorcraft.
I wonder if there is a lesson there...?
W.
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Wes wrote:

I have over the years bought a lot of parts from NAPA but had to quit using them. If you don't have your reciept for a return to another store or even the one you bought the item from you may well not get any consideration. After getting screwed that way I found out the stores are franchises and no internet customer file to look you up. I use O'Reilly auto parts now and their records cover Shucks customer history as well. Never an argument about returns anywhere in the country and they know every part you buy by bringing your file up on the system. They have quality parts as well and the choice of how much you want to spend and lifetime is available too and you don't need no steenking paperwork. http://www.oreillyauto.com/site/c/home.oap
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On 8/30/2010 11:28 PM, SMITH29 wrote:

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