Voltage problem

Also, 1970 probably has the older mechanical voltage regulator. Those are a large rectangular box with one terminal "FLD" w/ screw connection for the control wire (green?) going to the alternator. The later electronic Vreg's look much different, being flat with a triangular 2-wire connector. For the old type, you can buy a better electronic Vreg which has the same connectors for easy substitution, and will never need fussing with like the old ones. As 67Dart273 said, one electrical connection is to ground thru the case. The factory relied on a rusty sheet-metal screw, which was OK to meet the 3 year warranty. I ran a dedicated ground wire to the Vreg in all my cars. You see that today in most cars, along with many solid ground studs scattered around the car, since they found sheet-metal screws aren't reliable.