'78 Vette tach problems.

[Nickolas C.]

The tach has never worked since I have owned the car. Upon examination I found the circuit board damaged and ordered a new one. After installing, tach still doesn't work. Checked filter at rear of engine. Connection was proper at distributor and at end going to wire from fire wall. Disconnected both ends and hooked wire from fire wall direct to tach. Still nothing. Need help - any suggestions?

[Tom R.]

Re: '78 Vette tach problems.

The tach has never worked since I have owned the car. Upon examination I found the circuit board damaged and ordered a new one.

What was the damage to the circuit board? Crushed, burnted out? etc. It is estimated that 90% of time its the board but obviouisly you have moved beyond that guideline.

After installing, tach still doesn't work. Checked filter at rear of engine. Connection was proper at distributor and at end going to wire from fire wall. Disconnected both ends and hooked wire from fire wall direct to tach. Still nothing. Need help - any suggestions?

It will work without the filter but it sounds like it is not getting power. Is the needle registering anything? Sometime after the introduction, an inline fuse was introduced to protect the board...may have been 1977. I am not sure if it was later moved to the board or still inline for 1978. I'll look at my circuit schematic.

Finally, did your board come with insulation washers (fiberboard) and were they used? Or, the board should have had no solder around the mounting holes. New boards were shorting out because manufacturers did not understand that putting solder around the holes meant they would short. Than they introduced the fiber washers but did not tell owners to use the washers and why. Manufacturers have adjusted their board design to correct for this but it depends on their source.

This link is to an article that gets into technical nature of tach boards but not sure it has suggestions for your situation.

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

[Nickolas C.]

Re: '78 Vette tach problems.

Thanks for your reply. I ran across a thread posted by John Gardner about the fiberboard washers and tried that last night. It worked. Thanks for your help.

[Tom R.]

Re: '78 Vette tach problems.

My 78 is actually sporting one of John's boards. But I'm curious...who did you get your board from? PM me if you wish.