I have just tried to sort the timing on my 69 KG and the numbers on my digital Tach just jump about all over the place. This has also happened when using it on my 76 Bay but I have found that if I turn the engine off and on I can get a sensible reading for a few minutes before it goes hay wire. I am connecting the red to the - on the coil and the Black to the battery earth strap as per instructions. Is my Tach faulty or is there another explanation?
thanks
Will
On any electronic device -- be it a tach, battery charger, gauge, whatever -- the red wire goes to the + (Positive side), and the black wire goes to the earth/bare metal on the body, or in your case to the - (Negative side) of the coil. Look on the top of a Bosch coil, the + side is marked 15, and the - side is marked 1. You don't have to find the battery earth strap on a VW, which is in an out of the way place.
Maybe you made a typo and meant to write "the red to the + on the coil".
Randall
Not sure of the tach you have, but most have 3 wires. (Ground - Black), (12V - Red), and (POINTS - Green) (The points is the - side of the coil.)
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