The auxiliary cooling fan has 2 speeds - low and high. When the AC is on and the pressure at the dryer reaches 20 bar, the aux. fan switch (the one with the wires built into the switch S32 ) is supposed to activate the fan at low speed.
The high speed switch S25 , is only supposed to come at 105C.
S32 closes to ground and activates relay K10 .
You can jumper the wires together that go to S32 and see if your fan comes at at normal operating fan speed - low. Your Aux fan should come when you jumper the wire going to S32.
If the fan does , then you most likely have a bad S32, wiring issues or your pressure is low.
My AC system never achieves the pressures defined by the shop manual on the high side for the S32 aux fan switch , so I must assume that there is more to the pressure dynamics at the switch or I am misreading the shop manual info.
My Aux fan starts almost immediately when I start the AC system and my pressures are never above 17-18 bar.
The FSM shows a brown and a brown / blue from S32 to K10 and I verified that on my SDL. I would look to that circuit.

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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