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Not sure if this is in the right forum or not but if not, then I am sure that one of our wonderful moderators will tell me where to put it:D
I put my rebuilt alternator in this last Sunday and every thing seems to be working great. Charging up like my wife with her American Express card. Drove it Monday about 5 miles and every thing was great. Drove it todat and didn't seem to be charging at all and when I turned on the heater blower the Alt light slightly came on. Does this sound like a the Alternator or could the belt be loose (thought I gave it the 1/2 inch play test when I installed it) I can check the belt -which I think it is, later tonight but I am worried about driving it home tonight in the dark. Any ideas.
 

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Electrical problems are tough to find in person, really hard on the Internet.

It could be a lot of things: Alternator went bad (don't laugh), short, bad ground, bad battery.

Check your battery voltage (not running), check the charging voltage (just after start), check the voltage after running a few minutes. If these are OK, you're down to short, ground and battery (intermittent problem).

Battery: have tested, it's free.

Shorts and grounds can be discussed later, if that's the problem.

30 year old wiring stinks.
 

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baronbors said:
Not sure if this is in the right forum or not but if not, then I am sure that one of our wonderful moderators will tell me where to put it :D
I put my rebuilt alternator in this last Sunday and every thing seems to be working great. Charging up like my wife with her American Express card. Drove it Monday about 5 miles and every thing was great. Drove it todat and didn't seem to be charging at all and when I turned on the heater blower the Alt light slightly came on. Does this sound like a the Alternator or could the belt be loose (thought I gave it the 1/2 inch play test when I installed it) I can check the belt -which I think it is, later tonight but I am worried about driving it home tonight in the dark. Any ideas.
Are you absolutely sure you really want THIS! :D

Did you remember to put a ground lead between the alternator case and the engine block!!? REMEMBER that our alternators are mounted on rubber bushings at the bottom bracket and that the belt tension bracket is mounted with a rubber bushing at the timing cover, all for the sake of vibration isolation.

The operative word here is ISOLATION, as in, doesn't provide a ground path worth a crap! Stock wire (short, heavy brown, case to lower mounting bracket engine bolt) often gets outright tossed or just overlooked during reassembly. DON'T!!
 

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baronbors said:
Yah - I really want it- guess I'm just masochistic. Got a 6 gauge ground wire between the alternator and the block.
OK then, internal or external regulated? If Bosch external, original relay coil, points-type regulator or later transistorized "VW" regulator (potted, 1.5"x2.25" chrome can). Though original (metal can with yellow/tan tape around bottom) is required for "pure stock" and OK for everyday use, the later, transistorized version is a big improvement operationally, especially if stator has been upgraded for higher amperage.

Oh yeah, the ground wire is bolted to the engine by the rear bracket mounting bolt, NOT the bolt on which the alternator pivots, right? JUST checking . . . HAVE seen that before!
 

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ya the ground wire goes on one of the bolts that holds the lower bracket, not where the alternator pivots.
 

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If it is a one wire "self exciting" GM alternator that you have then sometimes the motor must be reved up to around 2,000 rpm in neutral to get the charging started. However the unit's case MUST be grounded to the battery as others have said AND MUST have its output wire correctly connected to the charging circuit without grounds or shorts or interuptions or the alternator will "excite" itself so much it will expire!
 
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