I hope I'm not teaching anyone's granma to suck eggs here, but some thoughts
on the subject.
Quoting "Gosling, Richard B" <Richard.Gosling@atkinsglobal.com>:
> It was also essential that
> the regulator was screwed down to a good earth, as it was earthed through
> the casing - normal procedure was to support it under the nut that retains
> the speedo.
>
> Maybe it is
> the case that a wire comes from the fuse, there is a spade connector
> part-way along for the regulator, then the wire continues to supply the
> indicator?
Yes, this is almost certainly how it should be interpreted. In general (-ve
earth cars) you have a long +ve voltage wire, and various components take a
spur and go to earth. When you see "oo, the fan is connected to the fan
switch on one terminal and the headlights on the other terminal" it normally
means the "headlights" connection is the +ve feed and if you follow it round
enough you'll get to the battery + or the ignition switch.
I don't know whether it's possible to destroy a voltage stabiliser by driving
the voltage the wrong way through it, but I'd check that if I were you. If
you've melted it, it's not going to work either way round now. If you have
faith that you have a decent stabiliser then Richard's point about a good
earth is valid and I'd also guess that the "extra" terminal is an earth.
Establish whether it is (do a web search on any serial numbers you can make
out on the casing) and if so connect it via a spade connector to the screw
that mounts the stabiliser to the body.
So your regulator wires up like this:
* Voltage supplied to stabiliser (some unstable mess of voltage)
* Voltage supplied BY stabiliser to gauges (nice and stable at a defined
voltage)
* Ground.
Once you are sure you have the stabiliser working and the right way round,
then the problem it likely between the stabiliser, the gauge that isn't
working correctly and that gauge's sensor unit.
The only other avenue of investigation that comes to mind is that the car may
have been (still be?) positive earth. This essentially means the electricity
goes the other way round the wires. It may be possible that one of the gauges
expects a positive earth and the other a negative. To find out which way
round the car is, check that the battery "-" terminal is connected to the body
or chassis. If so, it's negative earth. If the +ve terminal is connected,
you need to read up about converting! +ve earth is rare enough to be a
complete hassle if you've got it.
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