Ihave owned Benz's for 40 years and everyone was border-line hot running under the right conditions. I have wired many with a cabin switch with great results. Get stuck somewhere in traffic or such, and put it on . A NICE feature.
On yours , this is simply done by bridging the high pressure switch with the cabin switch at the a/c drier.This is the slow speed aux. fan circuit.
You can get into the high speed fan also with a little circuitry.