just wondering there i am meant to run the input wire from on a tacho? tried the coil and it read at idle but every time the revvs went up it petered out. anyone know there i should be getting the signal from?

Mine's on the coil, works OK. It's a 4cyl Volvo tacho, fits ...ok... in the spare dash hole instead of a clock. Perhaps the impedance or resistance of your cable is limiting the signal - since it happens at speed (I'm thinking some kind of capacitance effect like where the system can't respond quickly enough...). Maybe try another wire (mine's a 4 core phone cable, the idea being that I could hook up a temp sender or something (three other somethings) at some stage).

Cheers, Aurel.

The signal (green?) wire comes off the NEUTRAL/GROUND side of the coil.

My old analogue tacho had 4 wires.
red: 12v +ve power supply
black: -ve ground wire
white: dashlight for night time
green: signal from the engine

2 tips;
1/ make sure the signal wire is well insulated and doesn't rub on any sharp edges. If it shorts out it will ground the coil and stop the engine. Trust me, I know. The engine just dies for no apparent reason. Took me a week to trace the fault.
2/ make sure the switch on the back for '4 CYLINDERS', not 6 or 8.

was used on the old engine in the car, so should be set right, have run a fresh wire for it so shouldnt be any problems there but will check the connection.

thanks

mine came with it