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.
1. Solder one length of wire to the other end of each resistor.
2. Attach an alligator clip to each wire.
3. Mark the clips to prevent connecting them to the car reversed.
4. 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.