500SEL Defroster/blower issue
 

This is a 1985 500SEL US spec. If I turn on defroster nothing happens. If I stop car and turn it off, leaving defrost button in, when I go to start, blower comes on. But if I start it, fan shuts off.
What is going on here?

Im not sure but in the w124 e320 the start harness connects to the blower control which may not work to control the blower if its failed..but the car will not start without this blower controller installed. Ive had it out and the ignition system is dead wthout it..

And the blower system is automatically controlled with several inputs from the climate control including heat/ac/ and will come on high or turn off automatically when called for by given conditions..goes from low to high and off without changing the buttons..as temperatures change..

new ignition switch?
 

It turns out the blower does go on, but the ignition lock might be culprit. In the "on" position, the blower will come on . When I start car, blower shuts off, and blower stays off once car is running. But move the ignition key ever so slightly CCW while running, blower comes back on.

1985..so likely high miles and yes worn electrical contacts would not be a huge surprise at this point! Keep us posted