I was asked how to use the factory AC switch for fan control. I thought I’d share this with everyone.
You need to remove the white-green, white-yellow and white wires from the upper slider (shown in the picture). You can leave the yellow-red and brown wires untouched. Then you need to extend those three wire so that they reach the centre console. You can do the extension by soldering or with some connectors.
Then you need to connect them to the AC fan switch. All old wires from the AC switch must be removed first. The connector where the all red wire goes in factory AC installation should be connected to vehicle ground.
The following lists shows how the three wires from upper slider should replace the wires at the AC switch.
white-green -> red-green
white-yellow -> red-black
white -> red-white
The connector where green wire goes in factory setup can be left empty.
Before you put the battery back on please check that there are no red wires left in the AC switch in order not to generate sparks 😊
After this modification you control fan speed without adjusting the CR airbox valves towards blend valves at the same time.