Converting to 1 wire Delcotron alternator. Amp meter question ?

[BJB67530]

I'm converting to a one wire alternator. The wiring is simple enough, I have questions about the amp gauge. First of all I assume it's an amp gauge and not a volt gauge. It just says C and D. On a "normal amp gauge you just put it inline in the circuit. Will the factory amp gauge take that kind of load? How could it be wired so that is functional? Thanks for help in advanve.

[ray_mcavoy]

Welcome!

Yes, the factory battery gauge is an ammeter ... the "C" and "D" indicate charge and discharge respectively.

However, it is not your typical direct reading ammeter that is wired inline with the circuit. Instead, it is an external shunt type ammeter that reads the current flowing in the "shunt" wire that runs from the battery, across the radiator support, and connects to the voltage regulator (60-62 w/generator) or junction block on the horn relay (63-66 w/alternator).

So basically, the stock setup is only limited in it's current carrying capacity by the size of that "shunt" wire. I believe 12 gauge is stock on most trucks. But some that were equipped with higher output alternators from the factory used 10 gauge. There is a bit of a drawback to making this wire too large though ... it will reduce the meter's sensitivity to smaller currents.

Finally, the ammeter circuit on many of these trucks was un-fused from the factory and that makes it a bit dangerous. I highly recommend adding a couple of 4 amp inline fuses to the ammeter's lead-in wires like GM did with the 67+ trucks.

EDIT: I forgot to mention one important fact. In order for the stock ammeter to read correctly, the output of your alternator needs to go to the same point in the wiring as the output from the stock generator or alternator. If the output of the new alternator is connected to some other point in the system (such as directly to the battery) it will bypass the "shunt" wire and no longer indicate charging on the gauge.

[BJB67530]

As best I can tell it goes back to the external voltage regulator ( which I'm going to eliminate). This may take some study of the wiring diagram I guess.

[ray_mcavoy]

Do you have a 60-62 truck that was originally equipped with a generator? If so, the ammeter "shunt" wire was originally connected to the "B" terminal on the external voltage regulator which served as a junction point. If this is the case, you can install a stud type junction block in the old regulator location and use it to tie the "shunt" wire to the output from the new alternator.

However, if you have a 63-66 truck that was originally equipped with an externally regulated alternator, the "shunt" wire and stock alternator output were tied together at a junction / bus bar built into the OE horn relay. In this case that configuration can be left unchanged (aside from changing to heavier gauge wire if necessary).

[BJB67530]

I have a 1964 with an alternator. Unfortunately the wiring on the front end has been chopped on. Your reply helps. If I wire it back original and eliminate the external regulator it should work. I think I'll add the fuse as you suggested.

[ray_mcavoy]

Okay, here's a diagram I drew up for a page on my website showing how to convert from warning lights to gauges.
I know you already have gauges, but this diagram shows how the stock 64-66 wiring was originally configured. And it shows where to locate one of the 4 amp inline fuses I recommended.


In your case, just ignore the 4 wires connected to the external voltage regulator ... you won't need any of those with a 1-wire alternator.

Oh, and here is a diagram of the engine harness that plugs in over toward the passenger side of the firewall:

This wiring harness contains the other leg of the ammeter circuit (black wire going to the starter solenoid) that was originally left un-fused as well.
Adding a second inline fuse as shown here will help make the ammeter wiring much safer than it was from the factory.