[PDF] ˇ ˘ˇˆ - VDO Gauges Proper mounting with VDO’s Spin-Lokä Clamp or mounting bracket. Use this table if your tachometer signal comes from the alternator. b) light switch (also after the fuse in the fuse box); c) good ground location; d) location of the signal source (al- ternator, coil or other tachometer signal source).[PDF] Wire Diagram for VDO Small Tachometer - davebarton Black: Ground wire. Connects to “-” terminal on gauge. Also to side terminal on bulb. White or Gray: 12v power to bulb. Connects to center terminal on bulb. Goes to 12v positive light wire (brown color) in dash. Red/Blue or Blue: 12v power to gauge. Connects to “+” terminal on this gauge and to Fuse #13. Red/White or Red: Tach signal.