Why does my tach not work?
Potential Problems with a Tachometer A blown fuse is a potential problem with the tachometer. Check the fuses to ensure they are properly functioning. Bad wiring can also be the cause of a malfunctioning tachometer. If you are getting erratic readings, this can be a sign of bad wiring.
What makes a tachometer jump?
Usually a loose or failing switch will also cause the car to run poorly, but if the problem is very minor it can begin as an erratic tach signal. Look for corrosion, a broken wire, or a loose connection anywhere between the coil terminal and the tachometer.
What can I do about erratic tachometer needles?
SPA tachometers seem to be particularly sensitive to these spikes, but Auto Meter and Stack tachs seem to be much less affected. The fix is to add a simple 47k Ohm resistor (1/4 watt, 5% to 10%, rated to 500v) in the RPM signal wire from the coil to the tach.
Why does the tach needle keep moving up and down?
The tach needle bounces up and down instead of holding steady. If you hold the engine at a constant speed, the needle continues to move around. Shift lights fire at odd times, usually long before redline.
When does the needle return to normal motion?
Above 5000 RPM, the needle returns to a normal, smooth sweeping motion. It’s a very cool feature that vintage racers really appreciate. Many MSD systems (and similar ignition amplifiers) require a special tach adapter or even a special tach trigger in order to work with certain tachometers.
How does a Smiths chronometric mechanical tachometer work?
It uses a computer-controlled stepper motor to recreate the distinctive “tick-tick-tick” movement of the old Smiths Chronometric mechanical tachometer from the 1960s. Above 5000 RPM, the needle returns to a normal, smooth sweeping motion. It’s a very cool feature that vintage racers really appreciate.