2004 5.0L Merc... Tachometer not working

[KetchiMan]

I'm totally clueless about tach's and how they work. Mine has always worked fine, but now just reads about 800 RPM whether I'm at idle or at WOT, both while moving and while revving out of gear. Is there a sensor somewhere on the engine? Someone said maybe at the alternator?

I know absolutely nothing about this one, so any help is help.

Thanks.

 

[achris]

Re: 2004 5.0L Merc... Tachometer not working

Tacho gets its signal from the coil or ECU depending on the ignition system. By the sound of the symptom on yours, I'd say it' not getting power from the under-dash wiring... Check you have +12volts on the purple wire...

Chris..