Operation:

The electronic speedometer works by counting pulses generated from a pulse generator attached to the transmission ratio adapter, or by a magnetic sensor that counts teeth or holes on tone, slotted or other reluctor wheels. By setting the correct switch setting for your vehicle, you let the speedometer know how many pulses are in each mile. From this information, the speedometer will display the correct vehicle speed and odometer mileage.

Troubleshooting:

Electronic speedometers usually exhibit one of two different symptoms; wrong speed indicated or no speed indicated.

1. Wrong speed indicated – This problem usually occurs when the switch settings on the back of the speedometer are not set correctly for the vehicle’s pulses per mile. Using your speedometers installation instructions, re-calculate the vehicle’s pulses per mile and set the switches accordingly. Drive a known measured mile and verify the odometer moved 1.0 mile.
   Note: Sometimes when the speedometer is bench tested, the tester inadvertently leaves the pointer resting on the full-scale pointer stop. To fix this problem, install the speedometer and set the switches per the installation instructions. Drive the vehicle to approximately half the full-scale indicated speed and the pointer will “snap” to the correct speed.
   
   
2. No speed indicated
– First test to see if the ignition voltage is present at the speedometer. Using a multimeter, verify that the system voltage is present (12 or 24 volts DC depending on the vehicles ignition system) between the ignition and ground terminals of the speedometer. If the voltage is not present, troubleshoot the ignition and ground wires to the speedometer. If the voltage is present, if available, use a signal generator and input a frequency equal to the vehicles pulses per mile divided by 60. This should cause the speedometer pointer to deflect to 60 mp/h. If the speedometer does not react to the signal, replace the speedometer. If the speedometer does indicate 60 mp/h troubleshoot the speedometer sender and the wiring from the sender to the speedometer.