Okay now your car is looking pretty good. Maybe good enough so that your wife or girlfriend won't mind being see in it with you. One part of the equation was achieving a presentable appearance, now you need to have the car in reliable mechanical condition. Some mechanical repair and upgrading is very straightforward, rebuilding brakes, refurbishing the radiator and cooling system, getting the fuel and charging systems back up to snuff. Working on the motor and running gear. There are some problems that are not easy to diagnose and repair. Some electrical problems are hard to diagnose and repair. In my case some previous owner had attempted to fix a problem with the instrument panel and who knows what else by digging into the wiring harness behind the dash. I bought the car with the dash in place but not hooked up. The turn signal switch was broken, the printed circuit for gauges was mangled and some wires were disconnected and some poorly spliced.
With the help of a good wiring diagram I traced each of the circuits and eventually got almost all the functions back. I'm still having some minor problems that I'm chasing down. I've been told by some guys that I should just replace the entire wiring harness. Easier said than done. A replacement harness would be anywhere from one thousand dollars for an aftermarket replacement or almost fifteen hundred bucks for an OEM type replacement. That's more than I payed for the car. I have rewired a couple of motorcycles and one car, so I have some experience. I planned on taking my time and working on the essential systems first, the lights and turn signals, horn etc. So far so good. I had a problem with the charging system even though the previous owner had installed a new alternator and the regulator looked new also. I checked over the system and found that the alternator was not charging the battery. When I bypassed the regulator I found the alternator was putting out 14+ volts so I knew it was working. I checked the wires from the alternator to the regulator for connections and continuity and made some minor repairs. I found a really useful article in an old Musclecar Classics that covered the charging system. Using the info. I discovered that the two wires attached to the back of the alternator had been switched. Initially I had just attached them as I found them, which was wrong. I just made the assumption that they were connected right.
Generally I have not had a lot of electrical problems with prior cars. Even my 56 Cadillac was okay. I had a 66 Riviera that had a replacement ignition switch installed. I found an original switch in a wrecking yard and took the switch and harness plug and spliced it into my car. The problem usually occurs when someone opens up the harness to find a problem. Usually the harness is best left intact unless it has been chewed up by rats or has burned up by a fire. Most electrical problems are the result of a poor connection, faulty component or switch, or a poor ground. If a circuit is bad due to an unseen break, it is possible to run a couple of new wires outside of the harness to replace the defective circuit.