I own a 1954 Chevy Truck that was converted to 12V in an older restoration. The truck has been running quite fine and normally starts immediately. Here is my mystery...had a new clutch put in recently. Drove it home and parked in the garage. Noticed the brake light was not working so traced it to a disconnected wire under the dash. The running lights were not coming on so I traced it out with a meter and discovered the lights were wired but no voltage from the headlight switch, so made plans to see where the connection was bad. In the meantime, I ordered and replaced the 2 terminal strips on the inner fenders as the originals were loose on one end. Straightforward job to bolt them on and transfer the wires on lug at a time. Received a radio for the truck for Christmas and mounted it in the dash. Was planning to wire it to the ignition switch but when checking with the meter I could not find 12v. So started tracing. I checked the battery connection on the regulator on the firewall and only measures 3v. After removing the connected wires I reconnected one at a time. I connected the wire from the battery and measured 12v. Reconnected the next wire and still has 12V. Connected the wire from the alternator and the voltage dropped to 3V. This seemed unusual. With the alternator wire disconnected I measured 12V on the back of the headlight switch, however, nothing in the dash is working. No headlights, no gauge lights, no 12v to the coil ballast resistor. I tried to start the engine. Started turned the engine but no fire. I am an electrical engineer and have restored other vehicles but this one has me stumped at this point. I will check the battery voltage when turning on the headlights but if the battery is turning the starter I do not think it is the battery. Big mystery. Any ideas would be appreciated.