Erratic tachometer (rpm gauge)
 

My '93 has an erratic tachometer which jumps 1-2,000 rpms back and forth, but with no change in throttle position, or audible from the engine, or any sense of acceleration. I'm pretty sure its a ghost, and not actually jacking up the RPMs by 2000 in .03 seconds.

But I yield to those who may know better than I: is this a bug that others have seen? Where should I start looking; gauge cluster or elsewhere?
I can replace the gauge cluster but before I do I'd like to have some sense that the problem is in there (and not in the engine or trani or something)... and I have no intention of letting a mechanic spend 12 hours trying to diagnose it.

What say the experts on here?

I just replaced my gauge cluster because it started doing that, and after a while it just died all - together... at first the speedo, and then the tach, is how mine went, when I last pulled one of these apart, the winding in the motor for the tach / speedo, are tiny copper wire, with tension, wound on each end around plastic, and then going to welds on the PCB, either way the plastic expands and contracts with heat and causes the wire to get more / less tension, and eventually after 10+++ years fail... That's what it was for mine, dash clusters are not the greatest to remove / install as there's always a chance to break stuff, maybe buy/borrow yourself a "Ricer 12" Tach" just to double check, and for gods sake don't mount that thing just wire it and toss it in the passenger seat... or get a Apexi PFC, and compare that against what you see in the dash....

It's a common fault. I've also heard it can be a capacitor that blows as well. Mine would go all the way round to 9K and sit there and come back down etc.

Thanks for the added info. How was yours finally fixed; capacitor or other?

I'm considering just replacing the gauge for the tach and the temp; does anybody have a suggestion for source on these, which will fit in the cluster as a replacement. Not to change the whole cluster, just those two dials.

I don't want a digital temp reading, as that would be difficult for my wife to know that its too hot -- a dial would be better. I've seen the linearization procedure for the stock temp gauge, but thats WAY out of my league. A replacement analog dial would be best I think. Any suggestion are appreciated.

I had the irratic tach. Fixed it by fluxing and re-melting some solder joints and replacing capacitors as per this guide: http://www.wrex-racing.com/docs/fd/Tach_Repair.pdf

Taking the meter hood off is very difficult, more so than the guide lets on. I took a bicycle brake cable and slipped it behind and between the hood and dash. Then I wrapped each end around a screw driver handle and pulled to get it off. It's a bitch.

Also, be very careful removing the needle, you can pull the shaft out of the motor if you do it too many times. Don't pull on the needle with pliers, it is very fragile use your fingers gripping on either side of the hub and it will come off.

I've read that tach repair guide, but I just don't think I could manage it. Anybody on here want to do it for me (I'll mail you the cluster)? Or any shop who is known to do this repair job?