Gazehound

I just purchased a 1977 C3 and when I first looked at it, the Tach was working fine. When I bought it the Tach no longer works. I looked through the forum and found out it should have a low pass filter in line with the tach signal coming out of the HEI. There is no filter in line with BROWN tach wire coming off the HEI and heading through the firewall. My question is that I assume the previous owner removed it for some reason and pluged the brown tach wire into the HEI. Would running without the filter take out the Tach circuit board over time?

George Ries

Try a new filter corvette central has them

donyue

When I bought my 77 it did not have the tach filter attached and the tach works fine. I've had my 77 for almost 15 years.

If your tach stopped working then it might be the tach board itself as they have been known to fail over time.

Do a search or check with Willcox as they have some information on their site about testing and replacing the tach board.

Hope that helps!

oldC3guy

The tachometer in my '78 was fluctuating wildly. Over time I read in the Forum that it could be either the filter or the tach board. I decided to get a new filter. I figured this might be cheaper and easier to do than replacing the board. This solved my problem! Tach works fine now. If the problem had persisted, I would have moved to replacing the board.