Tacho pick-up point

[Warwick (Ozcoupe)]

Can anyone tell me please, where the tacho wiring pick-up points normally are on a 1970 model? The tacho is reading over double the correct reading.

The car has had Luminition (optical "points") fitted and has a late model Japanese alternator so one of these is probably causing the problem. I'd like to disconnect the tacho until I resolve the problem and would like to do it the easy way for preference; that is, without removing the instrument panel.

[Phil Nottingham]

The tacho picks up via an an ignition fed inductive loop on the back of it, another ignition fed supply is also present.

Use SEARCH se to a long time span for more info and pictures

[Warwick (Ozcoupe)]

Thanks Phil, I'll do that.

This is the first day that I've had a chance to have a good look under the dash and under the bonnet, in detail. I found a small unhappy-looking device in a metal case, with some fried wires attached. Disconnecting it stopped the fuel gauge and temp gauges from working.

Testing it with a multimeter showed it was a straight-through connection; doing nothing.

Do these 2 gauges have a voltage-regulated feed? Is this thing a voltage regulator? If it is it would explain the high readings on both gauges.

And, why not the oil pressure gauge too?

[Phil Nottingham]

That was the voltage regultor a standard Lucas device used on many cars of the 50-80's incl Land Rovers/Minis. Stabilised at 10volts I think

Do not use the instruments without it as they will burn out. Ensure there is no short circuit that caused the old unit to burn out before fitting a new one.

Th oil gauge works differently and is not as sensitive to voltage variations usually these under record due to hardening and eventual failure of a rubber diapragm in teh sender

[johnwp5bcoupe]

If you cant read your diagram very well this may help

s88.photobucket.com/albums/k163/johnwp5bcoupe/?action=view¤t=wiring.jpg

It looses a lot of deffinition uploading it if you want a better copy email me.

[Warwick (Ozcoupe)]

Thanks Phil and John; very helpful.
Hopefully the gauges haven't been damaged yet.

If this is one of those bi-metallic regulators that pulses on and off, would it be okay to replace it with a modern solid-state switch-mode regulator of sufficient output?

[Phil Nottingham]

Yes I think so