Its an adjustable microswitch fitted on the accelerator pedal on our drive by wire diesel. The actual variable resistor controlling the revs is the black bit at the top on the left.
The pedal has a lot of dead movement before anything happens and unscrewing this switch means the pedal is a lot more responsive.
However, doing this to get the pedal to what I consider the right position, the glow plug and Hold lights start flashing so I have set it back to it's original position until I know exactly what it's function is.
Still trying to find out how to alter the tick over speed as well.
