Wiring a three wire alternator up with factory ammeter gauge

[Harrison.]

I know the B/W wire coming from the firewall connection goes to the ammeter gauge, it appears a 12 gauge B/W wire would have gone to it on the engine side of the connector? My truck did not come with factory gauges and a generator, I am going to run a 3 wire alternator and putting factory gauges in. How do I need to wire it in? Will any hot lead work for the ammeter?

[dmjlambert]

The way the ammeter works is it measures the difference in voltage at the battery and at the main alternator output. So, connect one lead of the ammeter at the battery positive terminal after your fusible link, and the other lead of the ammeter at the alternator output. Both of those ammeter connection wires have a 4 amp fuse in them. The wire that goes between the battery and alternator is about 6 ft of 12 gauge wire, and it acts as the shunt for the ammeter. So that wire is part of the ammeter. Connect all accessories and everything powered in the truck at the alternator output, not the battery output.

You can see how the factory wired it in the wiring diagram.
http://67-72chevytrucks.com/vboard/s...27#post9186727

A fused black 18 gauge wire goes from the battery's fusible link output to the ammeter, and a fused black/white 20 gauge wire goes from a junction at the alternator to the ammeter. The 12 gauge red wire that runs along the top of the radiator between the battery and alternator is the shunt that makes the ammeter work.

[dmjlambert]

Adding the parts of the wiring diagram that concern the ammeter with other stuff dimmed out.



And inside the cab at the instrument cluster

[VetteVet]

Here's a link for you that will help explain all this and with the excellent advice of Mr DLLambert should get you started. You will have to make some wiring changes on the three gauge cluster plug to accommodate the gauge cluster, along with changing the temperature sender for the temperature gauge. We'll be here to help.

http://67-72chevytrucks.com/vboard/s...d.php?t=763180


Here's more on the battery gauge (ammeter)

http://67-72chevytrucks.com/vboard/s...d.php?t=393139


And a good one for the cluster conversion.

http://67-72chevytrucks.com/vboard/s...d.php?t=588853