brooksman9

If my Tach (that has been working) now stays pegged all the way up, is it shorted to ground or is the wire broke going to it. I know my temp sensor did this when it became detached, but I don't remember which way. Thanks

jpatrick636

It must be National Tach Problem Month. I just ran a couple of posts on tach problems and this is what I learned; it is most likely the tach filter. Check out this link http://forums.corvetteforum.com/zerothread?&id=849227&postid=1547657090# 1547657090

zwede

If it is pegged all the way up I would think it is the tach itself that is busted.

ACECO

When the tach filter goes bad, it's usually in a "open" condition. If this were the case (and assuming the tach itself is OK) then most likely it would just be at zero.

However that said these electronic tachs do have a habit of staying at the last rpm they were at when the power is removed. So assuming the tach was "spiked" just before the signal disappeared, then I suppose it's possible that the filter is open and the tach could be OK.

I suppose the only way to find out is to test further.

Good Luck!

brooksman9

Well, went out to start the car today and before I even tried I noticed the tach was back at zero. Cranked it up and it worked just fine. Guess I'll have to save this project for another day.

ACECO

As the tach filter is usually attached to the back of the intake manifold, and of course this gets hots during operation, perhaps the filter is intermittantly failing when hot??? If it does it again, you could always try detaching it from the manifold and see if that helps. However DO make sure you ground it somewhere or it will not operate properly.

FWIW. Good Luck!