Corvette 1975 Tachometer does not work ...... help!

[Steven B.]

We I put my 75 into hibernation over the Winter, the Tach was working perfectly. When I brought it out this Spring, it does not work. It reads between 1500 and 2000, and when I start the car, it initially moves about 300 rpms. I purchased a new repo tach filter and installed it, thinking that it may be the issue. No luck ................ any other ideas? A good friend of mine has offered to let me try his tach filter in place of the repo, but before I take him up on the offer, I have two concerns. 1. I am worried about causing his tach filter to be ruined, any ideas if I might cause his to break? 2. Does anyone have any other suggestions on correcting the issue at hand? Thanks to all who are reading this post and consider providing me with some advice.
Regards,
Steve

[Tom R.]

Re: Corvette 1975 Tachometer does not work ...... help!

It has been estimated that 90 percent of the time...it's the tach board which is a pain in the 75-77 models. The dash must be torn into to get at it. After 37 years, components fail and the circuit paths in those early boards were not robust enought to carry current and eventually burned out. Your board has had a good life! Another problem with the early board was that there was no inline fuse to protect the board...again, you board has had a good life! I include a link to an article written for the Corvette Enthusiast on C3 circuit board repair and replacement.

http://www.hunt4cleanair.net/Articles/tachboards.pdf

Also, the C3 Corvette Forum has had several discussions on this topic and vendors have posted how to access the 75-77 dash board to replace the tach board. I've included a link to a recent discussion by another 75 owner.

http://forums.corvetteforum.com/c3-t...3-75-tach.html

Hope this helps...keep us posted your outcome