sprinter based MH 4250k 2016

[road warrior]

i have what i would call adaquate brakes, not good, needing to stop such an almost permanent weight im a little concered about my upcoming visit to the Austrian Alps !, when i bought it the brakes were poor, but after front and back disks and pads we are upto adequate. Almost impossible to bow the front end and totally impossible to lock or wake up antilock. So, does anybody know where the weight distrubution valve is on a sprinter, as its left standing for at least 4-6 month a year, with week end - use, my feeling is the sensor is seized and therefore giving lots of bias to the rear - but im damned if i can find it - as its a commercial van as a factory build it must have one musnt it |?

Any help appreciated