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Old 05-22-2012, 09:40 PM   #3
ray_mcavoy
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Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,350
Re: 65 C10 alternator conversion w/external shunt ammeter?

Quote:
Originally Posted by VetteVet View Post
The ammeter will still work with the three wire alternator as long as it is wired correctly and the inline fuses are good. There are two wires that go to the ammeter from the charging circuit. One is a black wire that runs from the terminal junction on the passenger fender on the 67 to 72 trucks and I think on the older ones as well.

It will share the junction with the battery positive fusible link wire and the battery end of the shunt. The fuse is a four amp and is in a little football shaped holder. They are sometimes hard to find. The other wire is a black with white stripe and joins the alternator junction with the alternator end of the shunt wire and the wire that feeds the cab circuits.
These two wires run to the firewall connector and then to the dash plug. The shunt and the fuses are in this one.
Just for the record, the ammeter connection points are slightly different on the 64-66 trucks. The black wire goes to the battery post on the starter solenoid since these years don't have the junction block on the fender near the battery like 67-72. And the black w/white stripe wire goes to a buss bar / junction that's part of the horn relay (instead of an internal splice in the harness like 67-72). The 64-66 horn realy is out on the radiator support near the voltage regulator.

I've also found it curious that the 63-66 trucks didn't originally have those small inline fuses in the ammeter wiring like the 61-62 & 67-72 trucks. I don't know why they stopped using them in that time frame ... possibly some sort of ill conceived cost cutting measure. Adding them is a really good idea though. I've seen a number of 63-66 wiring harnesses with melted insulation on the ammeter wiring that was most likely due to an open circuit in the shunt wiring forcing the full current through the meter wiring.

Finally, the 66 & earlier trucks didn't have any fusible links from the factory either. So adding those would be a good idea as well.
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