Daimler tachometer and V12 badge
In my first drives of the Daimler, one of the things on my list to fix was the tachometer. When I first got the car, I had it converted to modern electronic ignition. The Jaguar V12 always had electronic ignition, however it originally used a system called OPUS. On my car, the ignition system had been messed with and the OPUS box wasn't working.
Instead of using OPUS, I had the car converted to a Pertronix LU-1122A. Instead of a separate ignition box in the vee of the V12, the Pertronix unit is completely inside the distributor. In period, the OPUS boxes used to overheat given their location, and were moved in later cars.
The Pertronix system has my car running very well, but the downside is that the Tachometer was no longer working. Unlike on the six cylinder cars, the V12s were always electronic ignition, so the distributor is already the right type. From my research, all I needed was to put a resistor between 9,000-10,000ohm between the negative terminal of the coil and the tachometer.
To work out how it was wired, I purchased a book that contained the wiring diagrams for the car. That helped me understand the purpose of the wires that went to the plug for the OPUS unit. I was able to identify which wire went to the Tachometer. Once Identified, I purchased a 9,500ohm resistor and made a line to go from the OPUS plug to the negative terminal on the coil.
I'm terrible at soldering, I so I used some connectors that need a heat gun to join the various wires, then put some heat shrink on top. Installation was quite simple, but unfortunately it didn't seem to work.
However, it turns out I had done it correctly, and when I had the car in the workshop, I had them check. It turns out that the wiring behind the tach was not connected properly, and once connected it all worked. Its been pretty reliable since, but occasionally it has stopped. I don't know why yet. Generally it works pretty well. I don't know if its 100% accurate, but then I doubt the tachometer ever was.
In addition, the other quick fix I did was to purchase the proper V12 badge for the centre console and use some trim adhesive to install it. A small thing, but it looks great in the interior.
