Tach Going Reverse - Help Please

[citmov]

So here's what's happening...
when I turn the key to acc position my tach jumps to 500. Then after I start it everything seems to appear okay. Idle sits at 1100 and after it warms up it drops below 1000. But when I rev the RPM to anything over 1500 the tach goes backwards below zero.

Here's a vid of what's happening:
http://youtu.be/L9Qbixt9fXg

Some more info on my car:
- 93LX 5.0
- No aftermarket tach
- I had a shift light attached when I bought it but I took it off to see if it was wired incorrectly but that did nothing.
- MSD dizzy (I had an oem before but did the same thing)
- MSD coil (this has been on every since I've had the car)
- New Ford racing wires
- New plugs

Any thoughts on what to check or what it could be? Any help would be appreciated. Thanks!

 

[jrichker]

The circuit board on the back ot the tach is toast. Good luck in finding a circuit diagram for the tach circuit board. I haven't been sucessful, but then again I haven't spent hours looking for it. If you can find a circuit diagram, for the tach circuit board, I will be glad to help you fix it.

 

[citmov]

Thanks jrichker for the reply!

So basically find another cluster?

 

[citmov]

It was the cluster (specifically the tach). Swapped out the cluster and all is well. Hopefully this can help someone if they run into the same problem.

 

[jrichker]

I ws hoping you found the tach board circuit diagram...

Glad you got it fixed.