So i got a used 95 impreza that sadly did not come with a tachometer, and i NEED to get one. Before i make the purchase i just wanted to make sure that i will be able to hook it up, and that even though it came without one, it still has the necessary wiring. And, what exactly is the purpose of the ignition coil besides being where the tach hooks up?
thanks a bunch for help!

Ignition coil receives signal from either the ECU or in the case of older vehicles the distributor. The coil then converts the low voltage to high voltage to fire the spark plugs. Older vehicles had high-tension spark plug wires going from the ignition coil to the individual plugs but some newer cars have no distributor and individual coil-on-spark plug systems that do away with spark plub wires entirely.

None of this really has any relevance to installing a tachometer as long as you have a place to source the ignition signal from, be it the ignition coil or the ECU. I think the signal wire is the negative terminal on the coil but it's been a long time since I've owned a car with one.

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k thanks, im sure my car is old enough to have the distibutor cap and ignition coil, so i bet ill be able to hook it up.

Find a used cluster with tach. from any 1993-96 Impreza and transplant the tach. into your cluster, removing the blank plate. The tach. will fit right in, no wiring needed.