tach is reading incorrectly

[bikeguy18]

Just recently my tach has started reading 3000 rpm at idle. It also doesn't move correctly when the engine accelerates. I've heard before that the tach gets its reading from the alternator. Is this true, and my alternator is going or could it just be a connection problem going into the tach. I've got 130k so the alternator is getting kinda old i suppose. Any other ideas on the cause? Thanks

 

[jimmiecakes]

Dave, the tach gets its trigger from the ignition system. Without some diagnostics to be sure, I can only guess at a faulty tach.

 

[sirhk100]

Mine did the exact same thing. First I pulled out the tach it self. Really easy to do, pull of all the trim pieces until you can actually touch the tach itself. Then litterally grab it and pull it out. There is a circuit board and 4 prongs attached to it. I cleaned all the contact points on the board and that helped a little bit so I figured it was definately the tach. My fix was to buy an entire instrument cluster off a guy on the board here for $40 and replace the tach. Now it works great. I think Ford wanted $75 for the tach and now I've got a whole set of spare guages including a tach that doesn't work. Check Ebay, there were some on there too when I was looking for one.

 

[bikeguy18]

Thanks for your help guys. I've looked around on the board and found some other posts from last year that addressed this problem and they pretty much came to the conclusion that it is the 4 prongs on the back. I'll give it a shot pulling it out and cleaning it, then go from there. Thanks again.