Where does one begin rewiring a car? For me, the answer wasn’t as hard as it may seem. That decision had been made months before. You see, during the research and education phase of this process, I’d done a lot of work to figure out what wiring harness would be the best fit for my car. Because the MGB and MGB GT were made nearly unchanged for almost 20 years, getting parts for them is still quite easy. And believe it or not, that includes getting brand new wiring harnesses. However, my car was not quite a factory spec car. As far as the electrical system was concerned, my car had an aftermarket air conditioner, a high-voltage coil, electric ignition system instead of a traditional distributor, and electronic speedometer instead of the stock system. Although to be honest, at the time I didn’t know about the high-voltage coil and electric ignition system. More on that later.
This meant that I wasn’t entirely sure if the stock wiring kit had all of the wires needed for my car. At the advice of the expert MG mechanic in town, I opted for a more generic wiring kit that was designed for those wanting to take any old car and bring it up to modern wiring. I looked at several different companies, and ultimately chose to go with a brand called Kwik Wire.
All of the wiring kits come with most of the wires connected to a central hub. That central hub is the fuse box that looks similar to the ones found in modern cars. So the first step was to determine where and how to mount the fuse box. The original fuse box was located in the engine compartment above the passenger side wheel well. Wires for the dash and interior components then went through the firewall on the passenger side and routed throughout the cabin. However, the new fuse box was designed to mount on the driver’s side of the car and was too big to mount in the engine bay. After a few failed methods, I finally found the perfect spot to mount the fuse box so that all of the wires for the dash could reach their respective instruments, and it would not impede any foot movements while getting into or driving the car.
Once the fuse box was mounted, the next step was to route various groupings to their respective area of the car. One reason I chose Kwik Wire was how easy they made this. Once the wires came out of the fuse box, they broke out into 70ish wires bundled into groups like Column Group, Headlight Group, Tail Group, Accessory Group, Motor Group, etc. I took each group and roughly routed them to their respective areas to ensure they would reach their intended destination. To further simplify the process, each wire was a separate color and pre-labeled by Kwik Wire with its intended use. For example, the Oil Pressure Sender wire was light blue, and the wire said Oil Pressure Sender every 3 inches down the entire length of the wire.
For the most part, this made the process easy of matching up the wires to the components in the car. Left headlight wire to the left headlight, right headlight wire to the right headlight, headlight switch wire to the headlight switch, etc. The wiring kit came with a detailed 70 page installation guide complete with pictures, checklists, and diagrams. Coupled with the diagrams from my MGB Electrical Systems book, notes I’d made while disconnecting the old wires, and photos I’d taken before disconnecting the old wires, I had no shortage of information helping me put this wiring puzzle together.
Over the next 6 weeks I meticulously went wire by wire, matching it up with the proper component, cutting the wire to length, attaching the proper connector to the wire, and then attaching the wire to the component. In addition to the wiring kit, every circuit had to have a grounding wire to be complete. Since it was likely a grounding issue that was the root of all the initial issues, I was extra careful to ensure there were plenty of ground locations around the car.
After working a few weekends on the car, spring break arrived. I decided to take a staycation from work and spend the majority of that week working on the car. During the process I discovered the car had even more issues than I initially realized. For example, this is when I realized that the reverse lights weren’t working not only because they were missing bulbs and not only because there was no wiring. I discovered there was no wiring because there was no reverse light switch installed on the transmission. So I had to source a switch from Europe and wait for it to be shipped before I could fix the reverse lights.
I started the rewire project on February 1st, and by March 18th I was nearing the home stretch! On Facebook I wrote:
I have everything wired up except for 4-5 wires that I wasn’t able to figure out. I’ll be researching those tomorrow and should be able to finish those up. Then I’ll be going through two different checklists to check and double check my work. If all goes well, I’ll have the battery back in it by the end of the weekend and will be able to start testing the systems. Fingers crossed!
Oh, I forgot to tell you that important detail. All of this time, I was working on the wiring and having no idea if anything I was doing actually worked. Because all of the wiring was connected and there were loose, unconnected wires, I couldn’t have a battery connected to the car during the job. It was only after every wire was connected and I’d triple checked each connection that I was able to put a battery in the car and actually test my work.
Ten days later on March 28th I wrote, “Just have to connect the starter relay and install the windshield washer system! #soclose.”
The following day on March 29th after putting well over 100 hours into the rewire project, the time finally arrived to put in the battery and start testing my work. All the reading, videos, research, user forums, and the gamble to do the project myself had been building to this moment.
Things did not go as I’d hoped. While the fuel pump, and reverse lights worked, nearly nothing else did. One headlight worked properly, the other did not. The blinkers didn’t work, the hazards didn’t work, the dome light didn’t work, the horn didn’t work, the wipers didn’t work, the brake lights didn’t work, and it engine wouldn’t even crank. After all that work, the car was in worse shape than before I’d started.
What a gut punch. I just sat there in the car in disbelief. I didn’t expect everything to work on this first round of testing, but I really didn’t expect SO MUCH of it to still be broken. I decided to go inside and walk away from the project. I needed to clear my head, take some time to relax, and get some separation from the whole thing.
After an hour or so, I went back out to the car and began troubleshooting each item one-by-one. I started with the headlights since one of them was working properly. I switched two of the wires, and boom, the second headlight came to life! And before long I had the horn, blinkers, and brake lights fixed too. Although it still wouldn’t start, I did get the engine to at least crank. So by the end of that first day of testing, most of the issues had been sorted out and were now working properly.
The next weekend I was able to get the dome light working, along with the heater, and air conditioner. It was about this time that I discovered the guts of the distributor had been replaced with an electric ignition system. I contacted the manufacturer of the system and they had me perform some tests. As it turned out, the ignition system was not working. To be honest, I probably fried the system by hooking it up incorrectly and then trying different wire combinations to see if I had something backwards. So I ordered a new system and patiently waited for it to arrive.
On April 8th the new ignition system arrived. I eagerly installed it and nervously hopped inside the car to see if that solved the problem.
I turned the key and the car immediately came to life! That moment was so exhilarating! I don’t know what it’s like to perform major surgery on a person and have that person come back to life, but I imagine that feeling might be similar to what I felt in that moment. All of the tension and stress was gone in an instant. It was ALIVE!!!
Once I got the car started, I spent the next weekend tidying up all the wiring, installing the radio, putting the center console and dashboard back in, and reinstalling the seats. Then on April 18th, 11 weeks after I first began the project, the car left the garage and saw sunshine again. It was a beautiful cool day with hardly a cloud in the sky. The bright red paint and polished chrome sparkled in the sunlight, and I’m pretty sure I had a bit more sparkle in my eyes and in my smile as I test drove her around my neighborhood.
What an adventure this project turned out to be. It exemplified the contrast between book experience and real-world experience. No matter how much I read or how many videos I watched, the best education was getting under the hood and doing real work. It also reminded me of how walking away from a gut punch moment to catch your breath and regroup is incredibly important.
Was the project worth it? If I had to do it all over again, would I make the same decision? Join me next week for those answers and more.
I’m Darrell Darnell, and this has been Stuff I Learned Yesterday episode 582, “Countdown to Ignition.” Stuff I Learned Yesterday is part of the Golden Spiral Media podcast network. Join me on Twitter at GSMPodcasts, Facebook, or our feedback page.