How are the three potentiometer terminals wired, and which one is the signal?
The centre terminal (wiper) of the potentiometer is the signal and connects to the yellow wire on the GS740-3P; one of the outer terminals goes to the green wire, that is the potentiometer GND. The input works ratiometrically over 0–3.3V. If the turning direction comes out reversed, swapping the two outer terminals is enough; the centre terminal always stays on the signal.
A potentiometer is a voltage divider: a reference voltage is applied across the two outer terminals and the centre terminal gives a fraction of that voltage.
Wiring:
- Centre terminal (wiper) → yellow. This is the control signal.
- One outer terminal → green (potentiometer GND).
- The other outer terminal connects to the reference terminal supplied by the system. One potentiometer is used per channel.
Practical notes:
- The input is ratiometric: what matters is the ratio, not the absolute voltage. For this reason it is important that the reference and GND come from the same source and that no chassis ground is picked up from intermediate points.
- If the direction is reversed, swap the two outer terminals. Never swap the centre terminal with an outer one.
- Solder and insulate the terminals; a loose wiper contact produces a fault where the speed jumps on its own.
- Route the cable separately from the supply and ignition harness, use shielded cable where possible and connect the shield to the green terminal.
The resistance value of the potentiometer is not stated in the product data; use the potentiometer supplied with the kit, do not substitute an arbitrary value.
Full topic: Electronic speed and throttle control on diesel engines