I have an 1983 300D and am trying to fix the tach which seems dead. I will try the silicon removal and cigarette butt fix, but one other concern is that someone cut the wires to the tach amp, butt spliced red wire to wires and shoved exposed ends into the female receptacle for the amp - I assume to make a good connection. The wire are shoved into pin holes # 2,3, and 6. Is this right? Can anyone point me in the direction of a wiring diagram of this device or know the pinouts?

Thanks
Doug