How is the upper speed limit taught with the blue wire on the GS740-3P?
On the GS740-3P the cable is first tightened so that it is taut at idle, then the engine is brought to its maximum working speed with the potentiometer and the blue wire is touched briefly to negative (GND). The green light flashes and, after about 8 seconds, the system does a throttle release-and-return and takes the upper limit into memory. The potentiometer then redistributes the range between idle and that upper speed as 0–100 percent.
Calibration is done separately for each channel. The steps:
- Connect the harness and seat the IP67 connectors fully by turning them.
- Set the potentiometer to its lowest position. With the engine at idle, tighten the cable to the throttle butterfly/lever so that it is taut; leave no slack.
- Using the potentiometer, bring the engine to the maximum speed you want it to run at.
- Touch the blue wire briefly to negative (GND). The green light starts to flash.
- After about 8 seconds the system does a throttle release-and-return; the upper limit has been stored.
After calibration, the whole rotation range of the potentiometer is distributed between idle and the taught upper speed. That is, the first and last parts of the potentiometer are no longer dead zones; the whole range becomes useful.
Caution: do not choose the upper limit above the engine's permitted maximum working speed. This setting is not an overspeed protection; it only determines the highest point the actuator can go to. The engine's overspeed protection, fuel shut-off and, if required, air shut-off valve must be present in its own system. Do not leave the blue wire connected to GND outside calibration.
Full topic: Electronic speed and throttle control on a diesel engine