PeachParts Mercedes-Benz Forum - View Single Post

jay_bob · #11 06-30-2016, 07:12 PM

The 240D manual control knob should be able to be mechanically adapted to use the speed pot. It would keep the stock look and be a nice upgrade.

The stock 240D fan control has 2 parts, a Bowden cable and electrical contacts.
Knob at 6:00, outside air flap totally shut, no power to fan
Between 6 and 9, flap opens, still no power to fan.
At 9, low speed fan (both resistors in circuit)
At 10:30, mid speed fan (one resistor bypassed)
At 12, high speed fan (both resistors bypassed)

If it was me I would delete the Bowden cable from the back of the fan switch and force the air flap open always.
Delete the electrical contacts (arrange the fan drive to always have power whenever the key is on).
Fit the speed pot to the back of the switch assembly. if you want to get fancy find a pot with the switch that actuates at the far CCW rotation, use that to drive a relay to the fan drive power to completely shut off the fan. If you go that route then you can use unswitched battery (circuit "30") on a new dedicated fuse to the contacts on the relay and set the relay coil up for switched power (circuit "15").