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.

Setup and Checking

1. To make sure the cluster is installed correctly, start by looking at the cluster. If it displays the time and your current mileage, then continue to the next step. If not, STOP and recheck the two plugs in the back of the cluster.

2. Insert the key, and start the vehicle. If you have done your work correctly, then you should see some LEDs illuminate as the engine speeds up to idle.

Understanding the Calibration Procedure

3. Since calibrating the Tachometer and the Speedometer are closely related, we will deal with RPM for now. Look at the graph below. Notice that there are two lines, one called Overall Circuit Setting and one called Actual Engine Output. For the Overall Circuit Setting line, the circuit board is designed to interpret voltage linearly with RPMs. This means that at 1000 RPMs, the circuit is expecting to receive 1.0 volts from the engine. At 2000 RPMs, the circuit is expecting to receive 2.0 volts from the engine, and so on. Unfortunately, this is not the case. The engine output is non-linear, which means that it does not respond on a ratio basis. You can actually see in the graph how the voltage output curves up and away, much different from the linear response of the circuit curve.

4. So in order to compensate for the non-linearity in the engine output, we have to adjust the circuit. What we want is a “Best Match” for the engine output. There are four control points for each segment, as you can see in the graph below.

5. By adjusting these points, we can make the circuit match the actual engine output, as illustrated below.

6. Adjusting R1 will change the overall slope of the circuit without affecting the other settings. This is useful when every setpoint is a bit low or a bit high.

Adjusting the setpoints for the RPM scale

Note: RPM calibration may be performed while the vehicle is in park or neutral.

7. Adjust R2 until the 0 RPM light illuminates.

8. Start the vehicle. As the tachometer needle moves, you should see a few LEDs illuminate.

9. Increase RPMs to a bit above 1800 RPMs. This is the end of the first 10-block segment. Adjust R5 as necessary to illuminate the necessary LEDs. Flex the throttle a bit until you are satisfied with the first 10 segments.

10. To calibrate the next 10 segments, increase RPMs to above 3800 RPMs. Adjust R3 as necessary to illuminate the correct LEDs. Flex the throttle a bit until you are satisfied with the first 20 segments.

11. 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 R4 as necessary to adjust the higher end of the scale.

12. You may need to repeat steps 7-12 to calibrate the scale, as some adjustments may affect others.