Non-Digital Tachometer Modification

Fig. 23 Non-Digital Tachometer Modification:

To improve the accuracy, and properly calibrate a non-digital tachometer to a transistorized ignition system, it is necessary to modify the positive lead of the meter.
The parts needed are:
2 - alligator clips
1 - 1000 ohm, 1 watt resistor
1 - 12,000 ohm, 1 watt resistor
2 - 1 foot lengths of wire

1 Solder one end of each resistor together, and solder this to the positive lead from the meter.
2 Solder one length of wire to the other end of each resistor.
3 Attach an alligator clip to each wire.
4 Mark the clips to prevent connecting them to the car reversed.
5 To connect the meter to the car:
a Connect the lead with the 1000 ohm resistor to the ignition coil terminal 1 (-).
b Connect the lead with the 12,000 ohm resistor to a good engine ground.
c Connect the negative lead from the meter to a good engine ground.