By David Ahrendt & Dean Sprague

David and Ann Deiner are fairly recent members of our club. They retired to Hickory, North Carolina from the San Diego, California area and among several other cars they are proud owners of a 1952 MGTD. David D. acquired this car from his Father who owned it since the mid-1960s. Apparently it is a very early 1952. It has the later sweep “curved glass” tach and speedo but still has the dash-mounted headlamp-dimming switch (instead of the button mounted in the foot well). Also, it was not equipped with turn indicators. David D. called David Ahrendt and me and asked if we could take a look at the wiring. It seems that it had a blown fuse and once it was reinstalled the car started but it would not stop running. Further, there were issues with the brake lights, running lights etc. We said no problem just brings it to my garage and David and I will take a look at it. Over the years having worked on many British cars we have developed some understanding of how they are wired. This is not to be so presumptuous to suggest that anyone completely understands British wiring. We like others before us just follow in the footsteps of Sir Joseph Lucas, the Prince of Darkness himself.

David D. arrived in his TD at 9:30 AM sharp and we were already there with test equipment and factory wiring diagrams in hand. We assumed this would be a relatively straightforward project-then David told us the story. It seems that some years ago his father decided to update the car and install turn indicators. He was struggling with it when his neighbor came over and offered to design and build something based on his unique electronic background that would “do the job”.

Let’s digress for a moment and describe the MG (Lucas) solution. It entailed mounting a mechanical relay box on the inside of the firewall. This device required hooking up 8 wires, which came from, the four corners, dash and firewall of the car, a flasher with a light on the dash and the use of double filament bulbs in the front and rear fender running/brake lights. It also had an indicator switch which employed a leather bellows designed to “leak” air slowly thereby creating a timer of sorts (of course they seldom worked very long), which was mounted along the bottom of the dash center. With the exception of the timer most of it while a bit convoluted, did work OK.

Now back to our project. Dave D. opened the left bonnet of his TD and then the firewall mounted toolbox to expose the solution created by his dad’s neighbor. First we had to open the weatherproof container (Tupperware) to get to the wiring. There it was, “spaghetti” wire laced with with diodes, relays, flashers, wire blocks and other sundry items all encapsulated in a household switch box cover plate safely nestled in that plastic Tupperware container. We immediately realized that we were looking at the work of someone with special powers beyond this earth and maybe a direct relative of the Prince himself, perhaps a Brother. We began trying to unravel this thing to determine how it actually functioned. I quickly decided that this was one of those things that I would never know everything I thought I knew about it. Whatever that means.

Here’s how David A. determined it was supposed to work and sort of did, he thinks. Since this TD still had single contact bulb holders in front fenders the neighbor devised a relay and blocking diode scheme to flash the running light as a turn signal. Of course he needed to split the wiring for the front lights and use a duplicate set of relays, diodes and flasher for the other side. The other half of each relay was wired to flash the rear stop lamp. There were two bulb indicator lights, a red and a green added to the dash to provide a jaunty nautical feel to the whole apparatus (port and starboard you know). This would probably have worked until something failed or the wiring fell apart. Naturally, there was no legible schematic and the Tupperware box was filled with mostly white wire attached with household wire nuts and bare connectors.

In the electronics world there are two theories, conventional flow and electron flow. Conventional flow theory came about during the discovery of electricity and states that electrons flow from positive to negative. Electron flow theory states that electrons flow from negative to positive. Electron flow is how things really work.
Now, in this case, with the various relays, diodes and flashers stuffed in that Tupperware box, this TD could possibly have both theories in effect at the same time. The multiple diodes caused some interesting back-feeding. Once the car was running the only way to stop it was to disconnect the battery. All lights illuminated whenever the brake pedal was pressed and since the headlights were connected to the running lights terminal at the dashboard switch this caused the headlights to come on as well. It must have been puzzling to have the TD behind or in front of you in traffic. In addition, you have the added benefit of no space left for tools in the tool box.

I suppose if we left the Tupperware contents in place, located a Flux Capacitor, and could get the TD up to 88 miles per hour perhaps we could go back in time and ask the neighbor what he was thinking. Or maybe go back even further and discuss this with Sir Joseph himself. We might find a Flux Capacitor but getting a TD up to 88 miles per hour would probably require driving it off a cliff. We don’t want to know that badly.

David D. decided that this unique design was something he could also live without so we ripped it out of the car and reconnected enough wires to get brake and running lights working again. He ordered all the parts required to recreate the original MG factory (Lucas) turn indicators. Fortunately you can now get the contact breaker relay box and flasher in electronic form. It looks exactly like the original but has increased performance and reliability (in theory). David Ahrendt has developed a special circuit diagram to facilitate the new installation. Of course this will require lots of new wire, hopefully in different colors this time. Should be a piece of cake right? Well, “only the Shadow knows” but we will keep you posted.