Hi Marc, thanks for your answer. The thyristor SCR1 is triggered long before the microswich bypass is activated. Nor when you turn on microswich bypass contactor M3 is activated, no signal on terminal B of the target Purple. The truck only works well at low speed, when we reached the halfway point of the accelerator SCR1 is ON, if a bit decelerate the engine continues at full speed, only stops if you release the gas pedal
Regards
Edgardo