Hello Maydon, Unfortunately, I am not a technical wizard like Brookes. For my video I just reported what resistance and voltage at the pins on my motorcycle were. The results lined up with values that I found on other BMW sites and literature. Fortunately my results indicated the tach was bad in my case. For you it appears there "may be" (maybe not) a wiring issue "somewhere" in the harness and that jumps well beyond my capabilities. Brookes might know more on the possible cause of the higher voltage. Just thinking out your results, it may not be bad that you are getting battery voltage at pin 10. The tach isn't looking for a voltage value (i don't think) rather it is looking at and counting pulses coming from the points. The signal wire sends voltage to the condenser and on up to the coils whenever the points are closed. When the points open the signal should stop. That voltage is coming from the condenser side of the bean can. Hmmm....do you still have a bean can? Maybe your condenser is sick, or your system is more sensitive on the meter and can actually sense 12.5 volts coming up the signal wire. If the signal wire was corrupted with a short someplace I have no idea what the voltage might read, but since you show resistance, I don't think there is a problem with a short in the wire (that signal wire has to go through some pretty intense environments on its way from the condenser up to the coils). Should you decide to try having the tach tested I would suggest going to Palo Alto Speedometer in California. I used them and they did a fantastic job. They really know what they are doing when it comes to our broken antique stuff. Hope that helps. Good luck. Contact me with any other questions you might have. Cheers, Rich. Be SAFE out there!

@@richardryer3412 Many thanks for your reply Richard. I forgot to add I have a R80RT from 1985 with electronic ignition. Not sure if that impacts the resistance/voltage I am looking for? The resistance I measured at pin 8 and 10 was .825 for both.

@@maydon0z I have the old bean can ignition from 1979 with a dual plug conversion. Not sure how that affects pin readings between our machines. May be time to send the tach in for a bench test. Hollywood or Palo Alto may do a free bench test. Never hurts to ask. Good luck. Cheers, Rich. Be SAFE out there!