Fitting an 82 gas PUP with a 65 amp GM alternator

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Fitting an 82 gas PUP with a 65 amp GM alternator

Postby thetundrawolf » Tue Jul 08, 2014 12:46 am

Having an E fan on my PUP put a draw on my stock 40 amp charging system.

I could take several trips before the battery began to get low, and eventually I need to jump it, or take it home and charge it.

So I went to a boneyard, and grabbed a Gm alternator with a v belt pulley, from an eighties era GM truck.

I took the alternator apart and cleaned it, inside and out, and lubricated the bearings. I made sure the cooling fins were clean.

Next, I put it next to the stock alternator, to scribe marks on the metal securing pieces.

I used the wrench to align the vbelt pullies. The GM alternator was slightly farther forward than the stock alternator, so I had to use a washer to set it back. ... 135654.jpg ... 134843.jpg

I could have done a better job cutting the pieces, but it worked fine.

So I took it for a test drive. The engine got hot, and it struggled to keep up. I noticed the pulley on the Gm alternator was smaller than the stock one, which means the alternator is spinning faster than the stock alternator.

On a chance, I removed the GM pulley, and the pulley from the stock Hitachi alternator, and they were interchangeable!

So I put the larger Hitachi pulley (That turns slower) on the GM alternator, and reinstalled the alternator.

A test drive revealed the motor was less labored, and did not get as hot. It was acting like it was when it had the stock alternator. Long term tests reveal it charges the battery perfectly.

A note...

As far as wiring goes, I could not figure out where to wire the "Sense" light, I even tried using the stock alternator light, but the engine kept running, even with the key out.

I finally wired it to a relay, that is controlled by a toggle switch, so I must release the toggle switch after I turn the ignition off for the motor to turn off.

If anyone has any suggestions on how to wire the "Sense" connection so that ti shuts off when I shut the key off, let me know.

Here is a schematic: ... 1291400434

Wiring it is easy. One wire goes to the battery terminal (not bridged, you can lose 1 volt bridging it) and the other goes to a switched +12VDC power source. The final connection goes directly to the battery to charge it. So it is self regulating.
1981 Gasoline PUP manual trans, 4x4
With an alternator from GM, an e-fan from Volvo, and a radiator from a Toyota!