Vdo 333-963 tachometer
My existing VDO tachometer has given up the ghost. I would like to replace it with a VDO 333-963, which is an electric tach with an integral hour meter. Furthermore, I would like to increment the new hour meter to match the existing hours on the engine, prior to installation.
Obviously, I will have to let the new tach sit on my workbench for 32.79 days (787 hours/24 hours per day) while attached to 12VDC, to allow the tach to accumulate 787 hours on the meter prior to installation.
Despite wiring up the tach in accordance with the VDO instructions, the hour meter refuses to increment as expected. So, does it need to sense rotation of the engine (ie-have an input from the rotational sensor simultaneous with the +12VDC from the start switch) for the hour meter to increment? Seems odd, as a conventional hour meter will happily tick along and increment hours if 12VDC is applied, just as it does in your boat whenever your ignition/start switch is energized.
I'm aware I can install a separate electric or mechanical hour meter (Hobbs, for instance), after adjusting it to read the desired hours. However, I don't want to drill another hole in my dash if I can help it. And yeah, I've queried VDO to no effect, and the vendor for the gauge has no clue.
I be confusticated. What don't I understand what I know about this thing?