GM Single Wire Alternator

These alternators work very well. And, because they really are single wire they look great and simplify installation. But there are a few things to be aware of before you connect this alternator up. Never dis-connect or connect an alternator with the battery connected! Get in the habit of removing the positive lead off the battery first! Internal regulated alternators have a nasty habit of blowing the diodes if the battery circuit gets shorted. If you blow a diode your battery will drain while sitting. In other words, you will have a dead battery the next time you go to crank it up. You can eliminate this problem by putting a relay between the alternator and the battery. Then activate the relay using the accessory post on your ignition switch. This isn't proper but will work. The only other solution is to replace the internal regulator, or alternator.  Now for some simple facts... even though this is a single wire alternator I would highly recommend your putting a ground wire from the case of the alternator to the battery ground. This insures a good ground connection and prevents a floating "positive" connection within the alternator(which by the way, will blow the diodes too).

Just so you will understand, a basic alternator has the cabability to produce over 100 volts AC and can push over a 100 Amps for a brief moment. Can you imagine what that would do to the rest of your electrical system? We are talking serous damage here... fortunately, the regualtor does a great job keeping the output in check. Now if the alternator does not have a real good ground connection the "reference" voltage the regulator "sees" will float up and down thus causing the regulator push more volts than really needed to properly charge the battery. This is also know as "Electromotive run-away" and it will fry your entire electrical system, if the alternator is not properly grounded!

Yes, I'm sure your engine is grounded, and the alternator is bolted to the block... but make no mistake, the resistance through that cast iron block, bolts, and brackets are no where as good as a small copper wire directly connected to the battery ground circuit.  

    by CBandit

      National T Bucket Association