A2K1

Hi

I am trying to make my tach work again. First step is to replace old tach filter with a self made one. But instead of one tach filter I found there two!

There is a write going to tach out of first tach filter and there is a wire that branches from it and goes into second tach filter.

I don't understand what that second filter and the wire that comes out of it are for. If I unplug that wire nothing changes except "check engine" light always stays on. I don't see that second filter on any wiring diagrams.

I am attaching a picture to make it more clear.

My car is 1980 C3 with new 350 engine and 3-speed auto transmission.

Can someone explain me please what that second filter is for and where does that wire go?
Where can I get wiring diagram for this car?

A2K1

I have checked wiring diagrams for my car and there should be no second tach filter and no second wire! This makes me think that there must be something else connected to that wire (to the green circle on the picture). Any idea what that could be?

DUB

The white wire coming off your distributor...that is plugged into the TACH area on your cap...has another white wire that has a brown female connector end on it. This is used for connecting test equipment while working in the engine compartment so you can see the RPM's when testing and repairing anything that requires watching the RPM's. Connecting 2 tach filters is not needed.

DUB

A2K1

I just found a different set of diagrams for my car. Mine is 1980 California car – it is different from non-California 1980s. It has a computer controlled Quadrajet carburetor, other C3s got them only in 1981.

According to diagrams the wire from ignition box goes DIRECTLY into tachometer. Another wire branches from it and goes to the engine control computer through the "tach" filter. I marked these two wires red on attached diagram.

Problem solved.