From: Philip J Ethier
> The schematic in the factory manual shows three connections:
> a double connection with both 12v in and out to the oil pressure gauge,
> green wires
> single connection to temperature gauge, green/lightgreen wire
> single connection to fuel gauge, green/lightgreen wire
> There is no mention of a connection to the case, or any ground ("earth"
> for our UK friends).
Does the shop manual or parts book show where it is normally mounted?
The hole in the tab is probably just the right size to sit on one of the
mounting lugs for the instruments - which are grounded so that the
lights can work.
> The temperature and fuel gauges appear to require stabilized voltage in
> all cases. I guess this means that there is a device to reduce the
> voltage from 12v to some lower figure and maintain it at that lower value
With engine running the system voltage is around 14V and really, who cares
whether the fuel level is shown correctly while the engine cranks. The
instrument probabably has sufficient damping of the needle that it takes
20sec to reach correct reading anyway.
> BTW, I have heard 10v, 6v and 4.5v as the voltage these things are
> supposed to regulate to. Anybody know?
You can probably buy each of those. The choice is forced by the instrument
manufacturer's requirement. I think that Lucas run at 10 or 11 volts and
that Bosch are lower, maybe 8V. What any others might be I couldn't guess.
I've had lots of Zener diodes die on the Excel, and always have a new one
in stock somewhere in the clutter of the garage. I'll try putting 14V
across old and new ones and see what emerges. Of course the late 60's
Europa instruments may be different. Or even, "Your voltage may vary"
Cheers,
Mike
|