Speedometer Calibration Procedure
Note: This is the most difficult part. To perform it safely will require two individuals; one to drive the vehicle, and one to calibrate the circuit board. It is VERY dangerous to attempt calibration while driving the vehicle alone. In additional, it is easiest to perform at night to see the LEDs.
Adjusting the setpoints for the speedometer scale
1. With the engine off, but the key in the ON position, adjust S4 until the 0 MPH light illuminates.
2. Start the engine, and begin to drive down a straight road with little traffic at a bit above 45 MPH.
3. Turn V2 as necessary until the appropriate LED illuminates for around 45 MPH.
4. Slow the vehicle down, and then speed up to 45 MPH to test the first 10 segments.
5. Find an infrequently used interstate that you can drive relatively fast but safely on and accelerate to as fast as you feel comfortable driving. (around 80-85 MPH works well).
6. Turn S2 as necessary until the appropriate LED illuminates for your current speed.
7. Slow the vehicle down, and then speed up to test the next couple of segments.
8. If you have calibrated the first 20 segments correctly, the last 10 segments should be pretty close. If you do need to adjust the last 10 segments, adjust S3 as necessary to adjust the higher end of the scale.