75 Electrical Questions

[synapse]

Greetings all, I am so glad I found this place... A little history

I have recently decided to give up on the "rolling plastic mistakes" that crowd our streets and cost a fortune to fix after sinking $4000 into my Xterra just for its 100,000 maintenance and decided to go back to my roots and pick up a beater.

A beater I did find... A 75 C10 shortbed stepside in need of some serious love, body is rough, interior is missing but i have been spending the last 2 months getting the motor and trans rebuilt and now it is making some nice horsepower and is quite fun to drive. I have been aquiring parts as I can find them on craigslist and ebay and tonight started on getting some safety issues resolved. Mainly no dash cluster, and no turn signals.

After spending a few hours on it tonight I got the turn signals working, and installed a instrument cluster I grabbed on ebay out of a 79. Tach works, fuel works, oil pressure works, Volts do not.

As I understand the 75 had a Amp gauge in it originally. So my first question is , what wiring changes need to happen to convert it to a Volt gauge? The wiring harness in this thing is rough, and looks like it was put together by a monkey with a butter knife, so any in depth info will help.

2nd question, which goes with the wiring harness being a mess. The dash lights all work, the only problem is that they work ALL the time! As soon as you turn on the ignition the dash lights come on. The light switch has no effect on them turning on and off or diming. The dimmer will turn on the dome light under the dash, but has no effect on the gauge lights or heater control lights.

Any help for this NEWBIE would be greatly appreciated