Need help with alternator

[RustyPile]

Originally Posted by vardenafil

I have a 72 k20 and I need to upgrade my alternator so I can run dual electric fans. The current alternator has 1 wire which from what I read means it's internally regulated. I also have on the front of my truck on the core support an external voltage regulator. When I first got my truck I had problems with dead batteries and once I replaced the external voltage regulator I haven’t had a problem since. So it makes me think it’s hooked up? The single wire from the alternator runs to the fire wall into a plastic harness I assume it goes to the relay inside the cab? I’m confused on what alternator I need to purchase. Do I just get a single wire one and use a thicker wire and run it from the alternator to the relay? Do I need to remove the external regulator or by-pass it as I’ve seen in a few forums

First, we need to determine exactly which alternator you currently have.. If, indeed, that voltage regulator is in the system, you'll have more than one wire on the alternator. Post a picture that shows the areas of the alternator where all the wires connect..

[B]"The single wire from the alternator runs to the fire wall into a plastic harness I assume it goes to the relay inside the cab?"[B]That wire is part of the main power distribution circuit. It has several "branches" that go everywhere. While we're on the subject: Go to the ELECTRICAL forum and download a copy of the electrical wiring diagram for your truck. It's the number one needed tool for electrical work.

You'll need an alternator output that will keep up with all the electrical demands. Typical radiator fans draw ~ 20 amps each. Air conditioning (if you have it) needs +/- 30 amps.. Lights, wipers, radio, and other electrical items will need another 15 amps approximately.. That's approximately 85 amps. A 100 amp alternator will provide enough "cushion" to keep the battery charged. If you insist on keeping that external voltage regulator, you'll more than likely need to have an alternator specially built.