When I start the car my tach spins all the way around once and then sits where ever it lands. I have been told that this is a short circuit problem or its just not grounding properly. However, my wiring schematic won't tell me the location of the tach ground. So, I would like to know if maybe someone else knows where the ground is and if its a short circuit, where does a short like this commonly occur?

 

where the cluster meets the harness, or the printed circuit board is fried, either way youre gonna have to pull the cluster out, but if your tach is acting weird the rest of your gauges should too

with me my tach was off about 1500 rpms, and it would never go below 2k, my battery showed a dead charge, fuel liked to dance around and my brights indicator would be half lit..

take a look at your cluster

 

the rest of the gauges seem to work properly. they don't skip around or anything and they do read properly, but if they are off they definately aren't off by much. the only one that seems to have problems is the tach.

 

ok when you pull the cluster itll look like this, see that yellow box with the wires extending across the cluster? It goes from the speedo to the tach and it controls the tach if i remember correctly, try looking there, pull the cluster and look for loose wires etc other than that id say just swap out the tach entirely, the stockers are reaallly cheap at junkyards and its not hard to swap, or you can go aftermarket

 

I think I'll pull the cluster out this weekend. I pulled the cluster out this past summer to check for loose wiring and I don't remember seeing that yellow box. I'll check it just to make sure, but I don't really want to get rid of this tach if I don't have to. My Firebird isn't really anything special being a base model and a V6. It's just something nice to drive, so stock is pretty much the way I'm going with it.

 

I pulled the cluster out and it looks like everything is intact. no loose wires to speak of on the cluster. I've read that the yellow box is the Vehicle Speed Sensor. If I were able to find one and replace it would that help?

 

The VSS has nothing to do with the tach. Just replace the tach head.

 

Where can you get a new tach head?

 

not to hijack the thread or anything but i have a weird tach issue as well have an 87 iroc and for some reason my tach is stuck at about 4500 rpm... now if i exceed 4500 rpm the tach moves normally but it never goes below 4500..... whats up with that??

 

Try this and see if it helps I bet it will.
https://www.thirdgen.org/forums/elec...meter-fix.html

 

no that doesnt help at all.. lol i mean that post is generally describing a short but if mine is reading (only after 4500 rpm) then i would assume that its not a short??.. i dont really know because i know nothing about capacitors resistors etc.

 

Not trying to hijack but got a quick question. What does the VSS do? Cause I swapped clusters a couple of weeks ago and noticed my old cluster didn't have one attached. Thanks.