So before I rip the speedo cluster out of my '88 I just thought I'd throw this out to see if anyone else had seen this before. My tach reads 1000 to 1200 higher than actual RPM's. I pluged my Brick (Snap-On MT2500) into it and my real time info is accurate, so it's the gauge- right?

I've never seen a liar tach before. Either they worked or they didn't. This is wierd.

 

That's the way the tachs in these cars ALWAYS fail. They read high.

It's not "1000-1200 RPM high"; it's high by a percentage. Let's say, 40%, just as an example; it's 400 RPM high at 1000 RPM actual, 800 RPM high at 2000 actual, 1200 high at 3000 actual, etc.

I have several tachs on my shelf. EVERY ONE reads high. One reads DOUBLE the actual RPM. The one in my car, was the closest to right out of all the ones I had, when I put it in. SOmehow I doubt it's still right. It's been several years, I bet it's readingi high by now too, like everybody else's.

Not the least bit weird at all, unfortunately. Very very ordinary.

 

The problem is due to faulty resistors in the tach board inside the cluster. If you can handle a bit of soldering it's not very hard to open up the cluster, take out the board and solder a variable resister in place of the blown resister which will allow you to literally calibrate your tachometer with the turn of a dial to match it up to a computer reading. That's what I did and now my stock tach is dead-on.

There is a really great thread on it if you search.

 

That sounds like what i need to do. Thanks.

 

Here's the link to the post.

 

OK-

I've read everything I could see in those links & from what I see there are two distinct setups: Pre '91, and '91-'92.

I've read through both of these & although I can make sense of most of it, much of it is too in depth for my minimal electrical expertise. What I noticed is that the discussion seemed to cross the lines back & forth between the two different cluster setups, which resulted in me being even more confused than before.

Riddle me this:

Can anyone spell out in idiots terms how to fix the tach on my '88, or connect me with someone who can fix it for me? I do have most of the required tools to do it myself, but I don't understand some of the electrical references & symbols, and once again I became confused which tach was which during the discussions. I'll fix it myself if I can get clear/concise instructions. If not I'll just ship it off to whomever is a pro at this.

Repairing my digital setups in my '85 & '87 Vettes was less aggrivating then this

 

I have a 91 RS with a 3.1 V6. Not only does my tach read about 400 rpm high at idle, all of my elecrical guages seem to read high. I have not reaearched it yet, but I think something is wrong with the power or ground connections. I thought it was funny when the car came with an extra instrument panel and there are a lot of Camaro insturment panels on eBay. I know that you can adjust the tach by changing the value of the resistors, but I do not think this fixes the root cause. This is definitely a common problem. I hope somebody solves it. Thank you all for all your efforts so far.