Open the blower cover and find the plug. Turn on the blower. Check for power.
There is apparently a resistor to keep something from overheating or something like that.
. R107 Parts Wanted: washer bottle
(1978), blue r107 visors, 107 trunk spare tire well, 107 headlight wiper arms w107 FS/trade/giveaway:
4 silver BBS RS009 8x16 et11 (won't fit front of 560sl without spacers and smaller lips), D-jet parts, 1975: (wiper motor, multiswitch, coil, injectors, etc.), US headlights, a black 1973 450sl