Question about tach................

[citruspilot]

My tach stays at about the 3500 RPM position with the key off and even stays about the same when the engine is running at idle. If I rev the engine up too more than 3500 RPM's it goes higher.

I have read that the tach is somewhat of a common problem with alot of the older Vettes and that you can change the tach circuit board easily to solve many problems, parts are about $55.00. If so is this circuit board replacement going to help my tach or is there something else that needs to be checked for this particular problem??

Thanks............

Jeff

 

[Copdogcorvettes]

That should fix the problem. The only other thing is the inline filter, but that should be part of your problem. I had the same problem with my 80 tach and the board fixed it.

Gary

 

[citruspilot]

Thanks Gary. I had heard of the inline filter but couldnt see how that would make the tach stay at 3500 RPM's. I'll install the curcuit board. By the way, where is that darn thing??


Jeff

 

[Copdogcorvettes]

It is on the back of the tach. You can not miss it. I think it has 2 or 3 hex screws that hold it onto the tach. The fun is getting the Speedo/ tach unit out to change it. It's not hard to do. Instruction come with the new board; LOOK READ DO.

Good luck and let us know how it goes.

Gary

 

[JOliver]

New board will more than likely fix your problem...few IC chips that burn out on them.
The 78-82 Speedo/Tach unit is very easy to remove compared to other years....few minutes and I can have one out...Three 1/4 screws hold the tach in after you get the front plastic bezel and lens off ...then there are 3 ,3/8" speed nuts that hold the plastic holder then 3 more on the board....I can answer any other question you might have on this matter ...email me at --------
VetteInstruments@aol.com


Jason

 

[80convertible]

If my memory serves me.... I had a tach problem about 3-4 years ago. I have learned to always check the easiest and least expensive things first. In this case I simply used a pencil eraser to clean all the contacts/connections and my tach worked perfectly. Remember, your car is now 23 years old. Corrosion will happen over time. After I repaired my tack, I went to cleaning all my instrument connections.

I have also read about people having problems with their tach only to discover that it was the tach filter. I don't currently have a tach filter on my vette, so I can't speak to it from personal experience. Maybe you should try disconnecting it to see what happens before you order the new circuit board. Again, try experimenting before ordering. If anything, you will get to know your vette better for later repairs.