A very common issue on the E39 is the failure of the final stage unit, also called the blower motor resister. This problem will cause the climate control fan to work intermittently, at only one speed, or all the time even when the car is off, thus draining the battery. Replacement part cost is under $100 and is a relatively easy fix to do yourself. Dealers will likely charge an excessive amount to replace this part so it is easier and cheaper to fix yourself. The part is located on the passenger side (drivers for right hand drive) to the left of the glove box, under the carpet that runs along the center console.
fuse 75 should go to electric fan, and fuse 76 should go to ac blower final stage blower resistor
bad blower switch located behind blower control.
Remove fan clutch with fan impeller. Remove A/C compressor drive belt. Remove cap from tensioning roller. Relieve tension on drive belt. Remove drive belt. Reverse procedure for installation.
According to the haynes manual it is under the glovbox on the blower box but it isn't theres in a 1998 BMW z3 and i am trying to research the location
u need a new blower
the blower resistor controls the fan speeds
Check the fuse and relay first. Then check the blower resister, then the blower motor itself. One of these is probably the cause of the failure.
check your fuse, check the wiring to the blower or the blower motor itself could be shot.
blower motor resistor needs to be replaced
Check your radiator fan switch and your fan switch coolant sensor .
Check the 30 amp Blower fuse. If not that check the fan relay, if not that check the blower motor directly from a jump on the fan itself.
Blown blower motor fuse? Bad resistor pack at blower motor? Bad fan switch?