Alternator problem

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Muad'Dib15

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I originally posted this in the early A body section, but I'm also posting here for more traffic.

So the alternator that was on the car yesterday was off of the 225 that was in the car originally. It was roughly 30 years old and was dying. I literally drove in the driveway after picking up a new alternator and the lights were dimming, it was raining today, I revved the car up and the lights brightened. I swapped it out in about 10 min and hooked it up and expected it to run. It fired for about 5 seconds then stopped. Ok, it does that every time I fire it up cold anyway. So I turn the key again and nothing happens. 30 min later it does the same thing. So 40 min before I have to leave for work I say screw it and put the old alternator back on. The car has been charging for about 4 hours because it needed it for some reason. Turn the key, nothing happens. While waiting for the car to charge for the second firing, I took off the dashboard and screwed the ignition down a little tighter so that it wouldn't turn when I turned the key. It sparked once. It also sparked when I put the wire over the bolt. The big difference between the two alternators is that the one I bought has two plugs on it and has a label that says it requires an external voltage regulator. I bought it for a 360 in a Plymouth "Fury", because it didn't come in 66 obviously. I'm taking it back tomorrow to get the correct one and to get the old one load tested. Did I screw up the alternator, and why won't it fire anymore? And could I have possibly fried the battery? Thanks.
 
The alt. with the two field connections needs one of them grounded in order to work with your regulator. If you got a higher amp unit you may want to also upgrade the charge wire or you could run into a problem (AKA fire). Also a swap to a solid state regulator or a newer setup. Otherwise get one for the correct year. Also you should get the battery load tested to make sure it is still any good. LA batteries don't tend to recover well from a big discharge many times.


Oh and any time you do electrical work disconnect the battery:toothy5:
 
I don't think your alternator problem has anything to do with the alternator, unless the battery is just "that dead"

The isolated field alternator you bought should work OK so far as a replacement --as cam64 said above. Just ground either of the field connectors and hook your existing regulator wire up to the second one.

It's POSSIBLE maybe even probable, that your problem is NOT the alternator at all. You may have problems with the bulkhead firewall connector, a loose connection somewhere, such as the rear of the ammeter, and all these cars have factory welded SPLICES in the main harness. These splices are subject to failurew
 
check the fusible link at the firewall/bulkhead connector too.
 
I replaced the alternator after getting the old one tested, it was bad, and got the car started. But before I owned the car, my grandfather apparently had a problem with the fusible link. My dad and I spliced it together, but now it cuts out occasionally. I think it's from the vibration of the car because it didn't do that before. So now, I'm thinking about getting a new fusible link then eventually just getting a new wiring harness all together.
 
Be careful at getting it tested at auto parts stores. I have had them tell me my alt is bad as it "only" puts out 30-40 amps. That is normal for this vintage. Head lights will dim at idle-thats normal. If it dims in the rain it maybe that your fan belt is to loose.
 
The lights were flickering constantly. You guys gotta realize that the alternator was at least 30 years old and had been sitting for 20 of those years. I'm getting a set of new matched fan belts as one is tight and the other is pretty sloppy despite the fact that they are from carquest, ours has really high quality parts especially compared to NAPA, and the same length. I guess it's just a fluke.

When I got it tested it failed the regulator and the rectifier test.
 
now my problem is different. I bought a new fusible link and ignition switch, dad told me to do that, and put the fuses in. I now have dash lights again, but now when I depress the high beams switch on the floor, the dash light turns on, but my headlights turn off.

It also has a windshield wiper problem. I turn it on and the wipers go, then freeze for a while then go again. Is that the switch being burned out or the wiper motor over heating? This car is from Birmingham, Alabama which has a lot of rain apparently
 
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