I know my aux fan comes on "high" at about 3/4 on my '90 535. I am waiting for a new fan clutch from BMA right now. The aux fan does cool it down for now, though. The clutch was definately "free-wheeling" after I shut the car down (not blowing enough air). I think you can jump the aux fan wires to see if "low" and "high" are working. Check that fan clutch, I think. Not sure about the water pump.