Replacing Electrical Wiring Harnesses On A 1968 Ford Mustang – San Diego, California

When it comes to websites, there is a 30 second rule. If you can’t crab the reader’s attention in that time frame, they’re gone. So maybe for some, they did not get to the part that said “I don’t repair original wiring harnesses. They’ve been in the car for over 40 years, so they lived a useful life. For some, they have been repaired just to get by for a few more years. And did you know that you can buy parts for your Classic Mustang at your friendly neighborhood hardware store? Don’t tell anyone that I told you that. Those household twist connectors are not designed for cars. They don’t make a real solid connection, and they do not keep out moisture very well. Also, if you’re going to replace any of the wiring on your stock harness, make sure it is the same gauge wiring as what is being replaced. The factory used specific gauges to handle a specific amperage. Electrical components and fuses in your car are all designed to handle a certain amperage. Altering the wire thickness can cause electrical issues.

This 1968 Ford Mustang had a charging issue, so I performed and electrical check. The volt meter would not move from 12 volts. I looked around for any obvious issues. I first noticed that the voltage regulator was unplugged, so I plugged it back in. No change. As I looked around the engine compartment, I noticed all the wiring was replaced with 10-12 gauge wiring, and were all the wrong color. At that point, there was nothing more to check, but to recommend replacing the under hood harnesses. Next, I checked all the firewall connections to make sure they were all correct. As it turned out, most of the stock under dash connection were altered or bypassed all together. I also found a lot of the wires were twisted together with duct tape wrapped around them, and there were twist-on connectors and splice connectors on many areas of the harness too. The main under dash forward needed to be replaced along with the convertible top harness. When replacing the harnesses, it is a good idea to replace most of the switches too. Wiper switches and heater switches can be left alone if they work. The ignition and headlight switches should be replaced. You do not want to replace a $200 harness due to a $20 switch.

The installation went relatively well up to the firewall, but then I opened one of the boxes. The main under dash harness was a 1965 Mustang in a box that was marked 1968. It’s real hard to plug rectangular bulkhead connector into round holes. A few days later, I installed the correct under dash harness, and everything worked like it rolled off of the assembly line. The charging system was reading over 12 volts, and the new harnesses took up a third of the space.

If you’re┬áhaving electrical issues, please give Classic Resto Garage a call at 619-929-8506 or email

Happy Cruising!


posted by inlinesix in 67-68 Mustang and have No Comments