trulytex

I have had problems with my Tachometer on my 1990 Vert since I bought it a year and a half ago. The tach registers EXTREMELY high - at idle it registers 6,000 RPM's. Well, I had a bad head gasket so the intake and heads were removed. I decided to go ahead and order a replacement tach filter from Corvette Central and install it while I had such good access to it. I will let y'all know if it fixes the problem. I took some pics of the tach filter location for those who have the same problem and want to see where it is located. Following are the pics:

juanathandavid

First of all, I thought this was a joke, such as muffler bearings, blinker fluid, cross-drilled brake lines, etc.

However, once I saw the pics, a light turned on in my head....I have seen that little thing before, and always wondered WTF it was! Thanks for sharing!

Tommy T-Bone

I have my cluster out and being rebuilt right now. If it's not in the cluster it's the tach filter. Thanks for the pointer. I have a 91 auto with the same problem but it has an MSD ignition box and that creates a whole new set of problems from what I read over in tech section. I just listen to the engine. The auto shifts.........automatically. .............

trulytex

Yeah, mine is an automatic too. But, unfortunately I am Super, Super **** (it sux & it's expensive ), everythig I own has to work perfectly and I maintain my "stuff" impeccably! This Tach Filter problem seems to really plague the 1990 Vettes so I thought I would post these pics to try to help anyone with this problem.

mechguy79

Thanks! I have a 1990 and it reads about 2k rpm high. I have already bought the replacement and will be installing it in a couple of weeks. This will really help!

jscdesigns

I have a 1990 also.. The Tach reads 2500 rpm at idle.. I change the tach filter and it didn't help.. What's the next step??

trulytex

I would say that the next step would be to remove your instrument cluster and send it off to be calibrated. I think that there is an advertisement for this in one of the Corvette supplier catalogs (Ecklers, Corvette Central, etc...). That would be my guess. I am hoping that the new tach filter will solve my problem, but now I am a little concerned. We'll see!

VtVette

I have the same issue with my 1990 cluster/harness. Bought a replacement tach filter and the tach still reads about 2.5K at idle.

trulytex

Where did you send your cluster? How much are they charging you? What's the turn around time?

Mine started out at around 2K RPM's too high and then it just got progressively worse as time went on. Now the Tach is pegged at 6K while at idle. If the new tach filter doesn't fix it, I guess that I will just learn to live with it or send it off to get recalibrated if it isn't too expensive.

mseven

I'm using a msd 6al and disconnected the filter (as per MSD instr.) and no issues.

trulytex

Well, the new tach filter is installed, but I won't know for a week or so if it fixed the problem, as the heads are still in the shop getting pressure tested and such. I spoke with a gentleman on the phone yesterday from corvettedashclusterservice.com and he said that I probably needed my cluster rebuilt (which he does) for $185, but then I noticed that he also sells just the tachometer module for $90.00 (http://www.corvettedashclusterservic...fo90to93.html). So I guess that I am curious - can I just buy the tachometer module and replace the old one for half of the cost. The rest of the gauges on the instrument cluster work fine. Any thoughts out there??????

Tommy T-Bone

I sent mine off to Southern Electronics. $325.00 to rebuild. Ecklers wants $399. Maybe I have the same tach problem with the 91. That one doesn't bother me as much as on the 90 6 speed.

Thanks mseven.

Tommy T-Bone

Got the cluster back and installed it. All the lights are now working and the tach is reading well. The LCD is a little dim in the daylight but at least I can read it. I ran out of gas because I couldn't read the fuel guage properly.All is well and cost me $325. That is the price for a cluster reconditioing and testing before return. Turn around time is about 2 weeks.

bill mcdonald

I am too

WVZR-1

The $90 Tach module is only the module. The calibration is handled by a "resistor network" chip on the mainboard. If your Tach "0's" with "key on" the module is likely fine. The mainboard needs some work. There are threads where this has been discussed and compared to earlier Corvette's and the F Body cars. The theory is the same but the fix is a bit more difficult. In the spring I believe I'll "tinker" with a "mainboard". I've been coached a bit and seem to think maybe I've 0'd in on the resistor to mess with. Not sure so I need to "tinker"!

trulytex

Well, the Vette is still in the shop getting the heads reworked. It should be out this week and I will see if the new tach-filter fixes the problem, but I doubt that it will. If that is the case, I will remove the cluster and send it to get fixed. Merry Christmas to me!

trulytex

Well, I got the Vette back today and the Tach is still messed up, so evidently the New Tach Filter did not solve the problem. I guess that I will send the Instrument Cluster out next week to be repaired. Just thought that I would keep this thread up to date. God Bless & Happy New Year to all (that means all Gens).

Red Tornado

honestly, i wouldn't spend any more $$ on this condition. i'd save the headaches, $300-$400, and keep it in the bank. you've got an auto trans, its not crucial. if you had a manual, i'd say its probably worth it. me, i would still let it go, and shift by ear/experience.

trulytex

I decided to push this thread back up for the gentleman who PM'd me today about this issue.

johnnyevans

If you have a high tach reading. 99.9999% of the time it is NOT the tach filter.
I've gone thru and checked / changed resistors, capacitors, chips till I got tired of it.
I think it is the tach head itself.
I replaced the 90 cluster with a 93 cluster, changing only the LCD crystal for the speedo / fuel gage and have no further problems since.
My convertible 90 has weird problems with the tach and I'm going to do the same.
I believe you can do the same with the 94 up cluster. You may have to repin a few of the idiot lamps. But tach and gages work the same way all the way up.