Gauge Cluster and Alternator Power

[broberson]

I'm completing the wiring for my 1970 C10, 383 stroker, AAW power plus 20 universal wiring harness. My question is this..
On the gauge cluster shown below in the top pic, slot #1 with the black/white wire, everything I've read says this goes to the alternator. Will this be ok with the power wire and the jumper from the #2 blade on the back of the alternator shown in the second pic? Just making sure. Thanks!

[VetteVet]

That wire is the left leg of the battery gauge and if you want the gauge to work you need it to connect to the junction of the alternator feed wire and the main terminal circuit of the truck harness. In the OEM wiring they had a shunt wire in the circuit which was calibrated to the battery gauge and the size, length and resistance were all factors in how well it worked. This diagram you posted does not meet that criteria so you may not get the results you want.

The advent of the internal regulated SI alternators came with GM going to a voltmeter in the gauge dash. I'm not sure what year, I think it was 74 or 75. The voltmeters do not need a shunt wire so that would not be a factor in the location of the gauge feed wire.

You might have better results if you connect the black/white gauge feed wire to the circuit branch 3 terminal. This would better mirror the original truck wiring. That wire as well as the other battery gauge wire are both positive connections and are fuse by a 4 amp fuse to protect the battery gauge.
See below.





The red wire on the left works as the shunt for the ammeter (battery gauge), and also serves as the charging wire for the battery.

I like the layout of the diagram you posted, but We don't recommend wiring the no 2 alternator terminal directly to the back of the alternator. The no. 2 terminal is the voltage sensing terminal that tells the alternator regulator what the system voltage is. and how much to charge the alternator fields depending on the amperage draw of the truck circuit loads. It won't compensate for the voltage drops in the wiring downstream from the alternator. It needs to be connected to a major terminal such as the circuit 3 connection which is fed directly by the alternator and it in turn feeds all the key switch circuit loads and any other full time hot or switched circuits as well.

I suspect that the two diagrams were merged and the top one is used to show how to use the battery gauge with a newer truck when converting to the internal regulated alternator. Which by the way, can be slightly modified to use the later model CS style alternators.

I hope I've helped.

[broberson]

VetteVet, you’ve helped tremendously over the past few years! If I’m looking something up, I always look for your name in the post for your two cents.

For the #1 pin on the gauge cluster, could I leave this attached at the bat post on the alternator, and run a new wire for the #2 pin on the alternator plug over to the junction block as you suggested? I don’t have a problem either way, whatever you think would work better.

Also, I checked the voltage with the current set up, and the reading was a little high at the battery. Something around 14.5 volts. Is that too high? Would this decrease if I changed the wiring to what you suggest?

Thanks for all your help, sir!
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[VetteVet]

For the #1 pin on the gauge cluster, could I leave this attached at the bat post on the alternator, and run a new wire for the #2 pin on the alternator plug over to the junction block as you suggested? I don’t have a problem either way, whatever you think would work better.

Yes you can try that and if the battery gauge doesn't work you can move it to the junction block and try that.

14.5 is good if it doesn't go higher than that at 2K rpm. turn on a few things like lights and heater and see what happens. It shouldn't drop below 13.7volts