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Vladgmru, Automotive Electrician
Category: Mercury
Satisfied Customers: 2668
Experience:  I've been working with American made cars since 1992.
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I have a 2000 Mercury Grand Marquis. I have an add on

Customer Question

I have a 2000 Mercury Grand Marquis. I have an add on electric tachometer for it. Trying to find out where to attach the green wire feed to the car. Looking it up on-line, it says to attach it to the IDM wire on the ignition coil. I can not find the ignition coil or the IDM wire....
Submitted: 1 year ago.
Category: Mercury
Expert:  Vladgmru replied 1 year ago.

Hello and welcome to JustAnswer.

My name is Vlad.

Your vehicle has 8 ignition coils ( each cylinder has a "coil on plug") that are controlled directly by the Powertrain Control Module.

It looks like you can not connect that electric tachometer to your car as there is no IDM wire or "tach" output wire on your car.

On older cars with a single ignition coil , a tachometer is usually connected to the "control" side of the coil.

On you car you have eight coils and I would not try to connect your tachometer to the "control" side of a coil for two reasons: 1) It could interfere with the Powertrain Control Module. 2) Even if it works, the tachometer may show wrong RPM unless it is designed to be connected for Coil on Plug systems.

Customer: replied 1 year ago.
I was told that installing a "Tach Adapter" would work. True?
Expert:  Vladgmru replied 1 year ago.

Hi, yes it is quite possible. I mean if they developed some kind of device that is intended to be connected to a "coil on plug" system so that you connect your tachometer to that adapter.

I know back to late 90's there were systems that used high voltage ignition leads to pick up pulses for tachometer purposes, but your car does not have ignition leads any more so it must be something that picks up injector or coil pulses and converts it into some king of signal that your tachometer can "understand".