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What did I do to my alternator?

4K views 3 replies 3 participants last post by  joe_padavano 
#1 ·
So I just had to replace the water pump on my '55 Caddy with a 331, and the one I replaced it with isn't quite the original factory dimensions and since I have converted over to an alternator I had to build new brackets to get clearance for the belt. Somehow while bumping it around trying to get everything to line up right, I seem to have killed my alternator. Any idea what I may have done to it? It's got 3 wires connected, 2 connectors on the side are a purple wire that I believe just goes to ground on the left & a brown wire that I have no clue where it goes on the right, and a thick wire going to the battery + terminal from a post on the back.

Those are the only wires right? I don't recall doing anything traumatic to the alternator like drop-kicking it across the driveway or anything, and those 3 wires are exactly as they were before when everything worked. About all I can think of is that it sits closer to the wheel well now than it used to, can't ground out over there can it? the case is already grounded anyway through the brackets mounting it to the block right? Seems like such a simple system I can't imagine what I screwed up.

Oh, I should mention what I've done so far to determine its dead. Voltage at the battery with the engine off is 12.67, with the engine on is 12.52, so the alternator isn't charging. No nasty noises though & it is spinning as it should.
 
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#3 ·
Hmm, it's definitely not wired like that link. My BAT Charging terminal on the back is going straight to the positive post of the battery, terminal 2 is the one that appears to be going to ground, and terminal 1 is the brown wire. I frankly have no idea where the horn relay even is, and I'm not sure whether I have an external voltage regulator as pictured or not...I'm thinking it's more like this one:
That diagram seems to indicate that terminal 2 should just be going to the battery + also or the horn relay if I figure out where the heck it is...and terminal 1 goes to the idiot light? If that's the case, when I get home from work if I run a jumper from terminal 2 to the Bat+ terminal on the back of it, that should give me a charge if the alternator is good, right?
 
#4 ·
Bill-E-BoB said:
It's got 3 wires connected, 2 connectors on the side are a purple wire that I believe just goes to ground on the left ...
:nono:

If the wire from the connector really goes to ground, you'v fried the voltage regulator inside the alternator. Assuming you have a 10SI style internal regulator alternator (a photo of the connector would help), that wire goes to the +12v junction block, same as the large wire from the threaded post. You can also simply run this wire directly to the threaded post on the alternator. This wire is supposed to be a voltage sensing wire, so it's better for it to run all the way to the junction block, but not mandatory. The brown wire goes to the GEN light on the dash and is required to be connected for the alternator to work properly. In addition to the link above, try this diagram:

 
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