Aquatec 550 12vDC pressure switch

DesertDweller

So I just hooked up mt Aquatec 550 booster pump which pulls water out of my cistern and into my pressure tank. It was being really noisy and wouldn't stop so I tried to adjust the internal pressure switch (the TINY allen set screw at the top). I turned it counterclockwise, which ended up shutting it off at 45 PSI. Not good! So when I tried to set it back, the allen had stripped and wouldn't turn.

I jerry-rigged a solution in the end. But does anybody know how to bypass this darn internal pressure switch and just use a regular external one?