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I am the 3rd owner of a 79 corvette and the tach does not work and I am not aware of what the previous owner tried or messed with. I already checked the clips behind the tachometer and one sends 12v and the other is a ground as they should be. After checking this I then bought a tach filter as I could not find one inside the engine bay and it appeared to be missing. With the way the tach is now when the car is off the needle sits at 2500 rpm and with the key turned it moves to zero. After started it then moves below 0 and when revved appears to try to go further under 0.
Not experienced with cars at all so I have no idea what could be wrong. Tried setting up a new tach tilter but wasn't sure of the correct way to attach it even with a diagram. Pic shows car how it is now and I am in need of assistance, any help would be appreciated and I will respond to any questions based off my knowledge of the car!
I agree the problem is not likely the filter. However can't imagine how the wiring polarity got reversed. sounds to me like you need a new tach board. all the vendors sell them. PITA to install however. put one in my 77 18 years ago. been working fine ever since.
I agree the problem is not likely the filter. However can't imagine how the wiring polarity got reversed. sounds to me like you need a new tach board. all the vendors sell them. PITA to install however. put one in my 77 18 years ago. been working fine ever since.
The answer is they can do all kind of weird things when a board goes bad. pretty simple setup outside of the board.
Power and ground, and just a tach signal wire going to it.
so, by the fact that it does try to move the needle, although backwards, it's fairly clear that it is getting a signal, just interpreting it wrong.
79 tach/tach filter
