Sgt.Gecko

Hi all, newbie here that just picked up a 1975 after a lifetime of second gen Camaro's. Anyway my newly acquired pride and joy has an issue with the tach. When the car is off the tach sits at 6000 and jumps to 6500 when I crank the engine. Once it starts it goes back to 6000 and doesn't move. I have always hated anything to do with electrical and am just looking at where to start. The only thing I've done so far was bypass the filter to see if that was the issue but it still did the same thing.

'75

Willcox has a lot of good info, here is some.

http://repairs.willcoxcorvette.com/1...-installation/

zwede

Most likely a bad tach board. Replacement boards are available, you don't need to buy the whole tach.

hunt4cleanair

Estimates are that 90 percent of the time, its the tach board. In 1978, the dash was redesigned for easier access to the tach board and circuit card. However, a 1975, requires removal of the dash to access the tach board.

Given that 1975 was the first year for the HEI (high-energy ignition), those boards used thin copper pathways that, over time, burn out. As well, components get brittle. Best bet is to purchase a new board with fresh components.

Check your dash bulbs before disassembly. In the event you have lights out, you can replace bulbs while you have the dash torn apart!

0Willcox Corvette

This is by far the easiest way to remove the dash pad from your car. Just follow the instructions and you'll be fine.

As Tom said above... my money is on the tach board.

http://repairs.willcoxcorvette.com/w...ad-removal.pdf

So once you replace the tach board you'll need to do what is called a zero set. The video below will show you how this is done.

http://repairs.willcoxcorvette.com/1...-installation/

Willcox

Sgt.Gecko

Thanks for the replies guys. Looking like a much bigger chore than I expected to get the tach out so guess I'll have to set some time aside.