Join Date: Dec 2001
Location: Belleville, Illinois
Thanked 22 Times in 17 Posts
The hookup you describe is close to correct. The problem is that it only will see the current coming from the alternator. To catch what's coming out of the battery and going everywhere else, you need to identify the wire doing that. It will be big, probably a 10, and come from the positive post of the battery or from the hot side of the solenoid and run to the fuse box or into the cab. It goes to the same terminal on the ammeter as the wire from the alternator.
An ammeter shows the volume of electricity going in and out of the battery, with the exception of what goes to the starter. To do that it needs to have all of the electricity flowing through it.
On mid-70s Jeeps there are two 10-gauge wires attached to the hot lug of the starter solenoid. One carries current to the fuse block and then everywhere in the Jeep. The other brings current from the alternator. Those two wires get removed and connected to one side of the ammeter. The other side of the ammeter goes to the lug on the solenoid, where the first two wires came from. tThat puts the meter in series with everything going in and out of the battery.
But that is somewhat dangerous and inconvenient because it means running two big un-fused wires through the firewall to the gauge. To avoid that there is a "remote shunt" meter. The shunt is a very low-value resistor that ges mounted next to the solenoid and is connected the same way as the regular meter. Then two small wires run from the shunt to the meter head in the cockpit. Remote shunt meters cost several times more, so they're not real common.