Need help with alternator

[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 itÂ’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 havenÂ’t had a problem since. So it makes me think itÂ’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? IÂ’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 IÂ’ve seen in a few forums

[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.

[PbFut]

I recomend you not do electric fans. I did 2 years ago. Very hard on the electrical system as designed nearly 60 years ago. Electric gives you little if any real lift over a correctly configured mechanical setup. If you must go electric, Powermaster makes very good alternators and will have the correct type. Internal, external and one wire, all in multi levels of power. Our electrical system was designed 55 years ago. The wire from main splice to fuse link close to the battery is too small for fans. If you connect at the main splice or horn relay, the fans pull too much from the jump to fuse link junction and you could over heat the main line or kill fans from low amps if alternator is not turning. If you connect at the fuse link junction, the battery Meter is confused by the hi amps being pulled at the wrong location in the harness and again the wire from main splice to fuse link junction is undersized and likely over heat if you run air lights and fan at same time..

[kwmech]

I agree on not using electrics. Electrics actually made my truck overheat. I went back to a clutch fan and shroud

[vardenafil]

I’m unable to use a mechanical fan. My engine sits too low and the fan shroud won’t line up with the engine. I tried replacing all the rubber mounts and engine mounts shimming etc…. I can’t get the engine raised enough.

[vardenafil]

I suck at getting pictures to attach. Hopefully this link

[HO455]

The link didn't work for me. I'm interested in what engine your truck has in it.

Here's some links that may help you.

First on 10si and 12si alternators the most common swaps on our trucks. It may help you identify yours.

http://www.madelectrical.com/electri...elcoremy.shtml

Second on how the externally regulated alternator and internally regulated alternators work.

http://www.madelectrical.com/electri...evymain1.shtml

http://www.madelectrical.com/electri...hreewire.shtml

How I converted my Burban. Starting at post 467.

http://67-72chevytrucks.com/vboard/s...or#post8564188

And lastly a thread on how to post photos from your computer that may help you.

http://67-72chevytrucks.com/vboard/s...d.php?t=627506

Good luck keep us posted on you progress.

[vardenafil]

I’ll have to upload images at work on Monday. I can’t get it to work off my phone

[RichardJ]

vardenafil, your link actually worked, but you edited your post and took the link down.
You have a 10si alternator which would have an internal regulator. You also have a voltage regulator which was used in the original 10 DN alternator.

You have a frick'n electrical mess.

Your truck is typical and the reason these trucks should not be converted to internally regulated alternators.
80% of the people doing anything electrical on '60s vehicles, don't have a clue in hell what they are doing.

[RichardJ]

your pictures.

[Stocker]

Six years ago I fought my electrical gremlins.... upgraded my alternator & wiring, and added 2 pusher fans. Here's a link to my thread https://67-72chevytrucks.com/vboard/...d.php?t=772236 in case you find it to be helpful. It's a lot of reading but contains a ton of good info from several great board members. Oh by the way, everything is still working perfectly since I did the upgrade.

[54blackhornet]

I would direct the OP to Mad Electrical . The site will bring you up to speed on the original wiring in your pickup. It also has a dedicated page on how to upgrade to an internal regulated alternator. They also have great components to greatly improve the efficiency of your electrical system…