One of the three channels does not work, the others are normal — where is the fault?
On the GS740-3P the three channels are completely independent and there is no communication between them; therefore one channel stopping is not a system fault but a problem with the wiring, potentiometer or servo belonging to that channel. The fastest diagnosis is to swap the potentiometer and wiring of a working channel with the suspect one and see which part the fault travels with.
Because the channels are independent, the cross-swap method is very effective:
- Swap the potentiometer. If the fault goes with the potentiometer, the culprit is the potentiometer or the signal cable.
- Swap the wiring. If the fault goes with the wiring, the 2 m line or the IP67 socket is at fault; make sure you have seated the sockets fully by turning them.
- Swap the servo. If the fault goes with the servo, the problem is on the actuator side.
- If none of them travels, look at the mechanical side: that engine's throttle lever may be seized or its cable may have slipped.
Additional checks: the supply voltage at the red and black terminals, smooth variation of the wiper voltage at the yellow terminal between 0-3.3V, and the green (pot GND) terminal being connected. Also, the memory of that channel may have been cleared; teach the upper limit again with the blue wire procedure. If the channel has gone into protection because of the current limit or the watchdog, resolve the mechanical strain first.
Full topic: Electronic speed and throttle control on diesel engines