Gauge wire to alternator

[dagnabbitt]

HI everyone, I am upgrading from idiot lights to the gauges package and although I have already found the very excellent post on how to wire that in (below, for anyone who needs it), I have just one question that I need clarification.

http://67-72chevytrucks.com/vboard/s...d.php?t=645940

What if I just wanted to run a wire from the gauge directly to the alternator without splicing into the light harness? Where on the alternator would I attached it? I've got two posts, as well as "R" and "F: tabs to choose from.

[HO455]

I am assuming your are referring to the amp meter. If so, for it to work properly the wire needs to go to the wire junction near the voltage regulator. The shunt amp meter only works correctly if the original resistance between each end of the gauge wiring is maintained. Moving the locations that the fused ends connect to will change that resistance.
A very small change in resistance in the circuit will cause it not to work or not work correctly. On my Burban changing the factory 12 guage wiring from the alternator to the splice and from the splice to the battery to 8 guage. Caused my amp meter to no longer work properly. If I turn everything possible in the truck the needle will only move about 1/32". I'm pretty sure if I experimented with some 1/2 ohm or smaller resistors I could get it working properly. But I decided to convert my amp meter to a voltmeter instead which was much quicker job. You may want to consider doing that too.
Good luck.

http://67-72chevytrucks.com/vboard/s...d.php?t=630289

[dagnabbitt]

Thanks, I have located the regulator (on the core support right?) and I will try to figure it out. I am a bit gun-shy with wiring, I've messed it before so I appreciate the assistance. It's a 1968, if anyone can tell me what color of wire it is that would be great otherwise I am sure I can figure it out.

[dmjlambert]

You can use any color wire you like. The colors of the wires they way the truck came from the factory are:
Terminal 1 on cluster: black with white stripe for the wire that goes to the alternator.
Terminal 12 on cluster: black with a brown stripe inside the cab, which connects to a solid black wire in the engine compartment to go to the terminal by the battery.

Both of these wires go through the bulkhead connector on the firewall in these positions. You can also use these positions if you get some male and female Packard 56 terminals. You can get at the connector inside the cab by taking loose the 2 screws that hold down the fuse box and move the fuse box out of the way. Unplug the engine and light harness from the bulkhead connector and install the new terminals (after you attach the wires to the terminals. Usually I crimp and solder the wires onto the terminals). The female terminals will slide and lock into the bulkhead connector. Inside the engine compartment, the male terminals will slide and lock into the connector. Then plug the engine and lights connector back into the bulkhead connector.


I do not believe the size of the wire is critical, so 18 or 20 gauge will be fine. One wire goes to the alternator Bat terminal (use a ring terminal and this is in addition to the 12 gauge red wire that goes there), and the other wire goes to the screw terminal on the passenger side fender near the battery (use a ring terminal there also). Use an in-line fuse holder near the alternator and near the battery on both of those wires, holding a 4 amp fuse.



Note that some people prefer a volt meter, and the author of that other post you gave the link to is TBONE1964 and he can probably outfit your new gauge cluster with a volt meter to replace the ammeter. The wiring will be simpler in that case because you would not need to run wires into the engine compartment.

There are vendors on the Internet that will sell you lengths of any color automotive wiring you want, including some with stripes. So if you want to make your new wiring same as or similar to factory wiring, you can do it.

Wiring diagrams for truck:
http://67-72chevytrucks.com/vboard/s...49#post7809749