Magic smoke escaping from alternator

[wikkid]

So I had my battery fully topped off, hooked it up, and immediately, without anything else, the alternator starts smoking (burning electrical smoke type, not Camels or Marlboros).

The car came with a spare alternator, so I brought it to a very good, local alternator place called Pasco - they tested it and said it was charging far too weakly. So I'm thinking of calling up Mark, and talking 95 amps.

Why in the world would an alternator do that, though? I hadn't even touched the car for a few weeks, so I had just topped off the battery charge so I could hook it up for some good noid light testing. I hadn't done anything else whatsoever to the car, and the battery had been out of the car for those few weeks, so absolutely dead - no current anywhere.

[spider2081]

Is there any chance you connected the battery backwards??? Connecting the battery reverse polarity will blow the diodes in an alternator.

[wikkid]

Hmm. No, but I wonder if the last thing I did on the car would have blown them: I was testing the injector signal with a noid light, so cranking the non-starting engine. The battery was draining, so I hooked up jumper cables - could the jolt of high-power juice fry these diodes?
In any case, I can get the alternator checked out at Pasco - if it is diode burnout, is this worth the fix? I'm on a budget, but the 95A alternator looks mighty fine, especially with those power windows, etc. on the '84...

[rlux4]

If you're getting spark at the plugs it wouldn't hurt anything, that's the same as if the engine were running. The voltage travels out the dist. cap to the plugs, no way for it to affect electronics elsewhere. Plus, a common method for checking for spark is to pull a plug, ground it on the block and crank the engine. Even this doesn't hurt anything because the spark just jumps between electrodes.
Ron

[majicwrench]

Methinks you had polarity wrong somewhere. You can actually even "charge" a battery backwards, so that the (-) is the (+). Guess how I know.
Keith