I had the same problem with an 89 740, take out the switch from the door and unpluc the electrical connector.

you will have to remove the switch unit from the mounting plate which should leave you with just the rocker switch.

from the bottom use a thin straight edge screwdriver and release the retaining clips and slowwllyy pull the unit appart, there are two small ball bearings inside so be careful you dont loose them, clean up the contacts with some wire woll abrasive paper or whatever u got ( i just scrached them with a screwdriver untill they were clean.

reverse the rocking contact so the central pin on the switch base makes contact with a clean bit of metal on the rocker contact.

place the BBs in the centre of the rocker contacts and push the unit back together. when u push the unit bak together make suer the swithc is in the central position or it may jam


Cheers ian