My tach died a few weeks ago and I got the unit repaired by Palo Alto Speedometer. I hooked up the wiring according to my notes from removing my old unit. Unfortunately, the rebuilt tach is not behaving right. The needle movement is erratic. At idle, the needle is off scale at the low end and the needle is jumping around when I rev the engine. The engine stumbles and misses as well. I suppose the first thing to do is suspect that I got the wiring mixed up, but I was very careful when I took my notes. Here is a drawing of back of the tach showing how I connected the wires. The car is a 1972 911T. As far as I know, the car is stock.
The first color is the wire color while the second color is the band (ie., White/Blue is a white wire with blue banding).
Can anyone tell me if the wiring schematic would be correct for this year car?
Thanks
Steve