Step 1: Take It Apart
Give the rest a good cleaning.
I opened the switch with a pryer to check the possibilities on the lighting. Four positions were possible: all off // all on // 1+2 on, 3 off // 1+3 on, 2 off
Step 2: Have a Break and Listen to the Radio
Step 3: Reassembly and Wiring
The four positions were: all off // 1+2 on, 3 off // 1+3 on, 2 off // all on So number one got the lower Watt the others the brighter ones.
I fixed the light sockets to the existing fixtures, so that the bulbs didn't get to close to the housing. The wiring was a bit try and error, but it finally worked out to my liking.