When the car is warm and driving at speeds greater than 25ish mph, the blower motor does not turn on. For example, on my morning commute I start the car up with the blower off. I then get going, letting the engine warm up and keeping my speed around 40mph. After about two miles, the engine becomes warm enough that the blower should turn on, and it will if I stop in the middle of the highway. However, since most mornings I don't have a death wish, it doesn't turn on until I slow to a stop at the next stop light another 7 miles away. It does this predictably and without fail. If I turn it off after it's been running, it will remain off until I come to a near stop again. The fuses all look good. Those icy 7 miles of my morning commute are brutal in this Wisconsin cold.

Does the blower come on immediately if you select defrost? Good used blower motors are so easily available and replaced that I'd swap it just to see if it's tired bearings or worn brushes. Maybe there's a forum member near you with a spare.

Sixto
87 300D

What car?

__________________
83 SD

84 CD

It's a 87 300SDL.

Often times the push button unit itself, over time, acquires cold solders.

To be sure, you'll need to pull the unit and check the pc board.

__________________
83 SD

84 CD