Chevrolet Repair: electrical system 1973 chevrolet 3/4 ton V-8, don loomis, battery voltage


Question
My son bought a 1973 C-20 pick-up.  He didn't have it checked out properly, (he was 17 then) and basically got robbed.
I am divorced and he was 700 miles away and I had no part in this transaction.
Now when he came to visit me I replaced the radiator, (it leaked), the alternator, (it was worn out), and the battery, (it wouldn't hold a charge).
It seemed to work fine after that but the battery keeps draining.  With a good alternator and battery where do you look next?  Voltage regulator?
I realize there must be something draining the battery and it's especially severe when operating at night with the lights on.  From a full charge it will drain to the point where the starter doesn't turn over in about two hours.
That happened last night and I pulled the battery, charged it, and today we will go get the truck and bring it back to my house.
If you could give me a place to start in troubleshooting this problem I would be very happy.
I have a good voltmeter and plenty of tools so any advice will be appreciated.

Thank You,
Most Sincerely,
Don Loomis

My son is in the Marines now and they frown upon car on base that don't work properly.


Answer
Hi Don, It sounds to me like the alternator isn't charging. I would replace the regulator too. After you do that make sure that the battery voltage goes from 12 volts (engine off) to at least 13.5 volts when you start the engine.

Hope this helps you

Mark