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Tachometer (rpm Gauge) Please help

I have an 2004 f150 heritage was trying to put an aftermarket tachometer in it got every thing hooked up except the tach signal wire instructions say to hook it up to the coil but this truck has many coils Does any one know how to locate a factory tach signal wire in the truck . any suggestion is usefull

The factory tach might get its signal from one of the coils.
Any one of the coils will do the trick, but an aftermarket tach will read low by a factor of the number of coils.
So if there are 4 coils the tach will read 500rpm when the motor spins 2000rpm.
Each coil will make 1/4 of the ignition pulses.
The factory tach compensates for this.

OTOH the factory tach might get its signal from the crank position sensor or the computer.
That signal is likely incompatible with an “old school” tach.

Good luck.

The factory tach gets it signal from digital data that is sent to it by the engine computer.

So there should be a wire with a signal in the dash right? Does anyone know how to find it? Thanks for your response.

Don’t hook that thing up anywhere on the truck. It’s not compatible.

You aren’t understanding. The same wire carries data for the engine temperature, and a whole bunch of other stuff. It is not the kind of signal that you can just hook to a gauge. It has to go to a micro-computer, such as is in the instrument cluster of your truck.

According to http://www.autometer.com/cat_accessoriesdetail.aspx?vid=99, you’ll need an adapter, and then you’ll need to cut a wire in your wiring harness to install it.

If it was a tap-on connection, I’d do it, but not for a cut and splice. I think you may want to reconsider.