What's up guys? I have a 93 SE 5spd with a aftermarket tach & shift light mounted on my steering column, all the connectors are connected to this tach. But for some weird reason my factory dashboard tach still moves. Not really with the rev's of the engine but it just crazily spins and jumps when it wants to. One time I was topping out on the highway and after I hit 120mph it just started spinning back and forward.
What could be causing this?

 

Wind? lol mine moves around a litte cause I took off that plastic guard, it was scratched up

 

probably the wiring of your aftermarket tach. Double check the wiring, and it would probably be best to run it seperate of the stock cluster.

Also you might want to unhook all the aftermarket wiring you did and check the stock tach again, if it does it with nothing else hooked up then you know its something with the factory tach, but if it only does it with the aftermarket tach, then you know the aftermarket tach is causing problems.

depending on what brand and cost, if you want to sell your aftermarket one lmk, my mustang doesnt have a tach in it, and it sure would be nice to know just how high I am spinning it.

 

I had the same idea about trying without the aftermarket tach but it still was going crazy, I just can't figure it out. I really don't think its wind.