i have a 88 firebird after motor swap it will not charge ive tried 4 different alt no broke wires anyone know if there is a hidden fuse im missing it was charging find before engine swap im so lost where i bought then engine was a local engine shop they said it was a 305 couple guys i talk to said it was a 350 why this would matter im curious if it could be a computer promblem why it is not charging dont see how , starts runs great i just cant get it to charge , i did take a wire and run straight for back of alt to the battery and it was charging anyone have any ideal im so desperate

 

Make sure you're supplying 12V to the field post on the alternator (alternators need an exciter filed to work) UNLESS it is a one- wire alternator.

 

Your alternator could very well be a one- wire. And I don't know how they get the exciter field going with only one wire, unless they backfeed it. But normally on a three- wire setup you have a ground post, a field post, and a battery (output from the alternator) post. You may have a blade plug with several wires in it rather than the posts.
I believe that 12 volts from the ignition switch will go to the field post as soon as the ignition is turned on. This provides an exciter field that the alternator needs to produce voltage. No field excitement- no output voltage.

I'm not the best on electical systems, and most of the stuff I do work on is older stuff. But I do know that you need an exciter field for the alternator. I hope this helps a little. Maybe a better electrician will jump in too!

 

well thanks the plug on top has 3wires in it one red wire on the rear of alt i was not sure if there was some kind of jumper i could hook to the alt to make it charge or not? thanks for you input i can turn nuts n screws this alt has me puzzled

 

I don't want to tell you the wrong thing and have you burn up your alternator, so take this with a grain of salt!

If you also have a black wire, I would think that would be ground. So you MIGHT- CAREFULLY try putting a jumper from a hot wire or the battery to whatever other wire is there and see if it works. Better yet, first get a cheap 12 volt trouble light or a VOM meter and troubleshoot that other wire to see if it gets 12 volts when you turn the key to the ON (you shouldn't need to START) position.
Let us know what you find out!

 

And I forgot- you have to wonder why you would lose your charging system after doing the engine change out. You wouldn't think that would be a problem if everything worked before the engine change.

But as I tell my sons, "strange things can happen, and quite often do". Who ever would have thought 10 years ago that somebody would fly perfectly good airliners into giant skyscrapers? And yet it happened!

One simple thing comes to mind, check your plug connection for pulled out wires or folded over blades or pins from when it was re- connected. Good Luck!

 

thats the thing original alt was fine ive tried 3 others since dont know why the motor swap stop the alt there is fuse links on starter all look good i geuss i should check them with a tester dont see why motor swap would mess with the fuse links