A while back I installed an M3 microfilter cowl. The only thing that I never adressed was the AUC sensor, the stock wiring harness is too short for the sensor to mount into the cowl. The AUC sensor is a sensor that detects the particles in the air, and controls the automatic recirculation for the HVAC. I have not found the system to be particularly effective and is a pretty usless sensor. Nevertheless, it would be nice to mount the sensor in the proper location rather than just dangling in the brake booster area.
Luckily, most automotive connectors used in German cars can be disassembled, repair or modified. I removed the 3 pin plug off the harness and made up an extension harness with MQS pins. This allowed the existing pins in the harness to plug into my extension harness, which I encased in heatshrink. I then attached the old connector plug onto the extension harness.
The sensor now can be mounted onto the M3 microfilter cowl, minor detail but nice to have it attached properly. I have not noticed any improvement in the auto re circulation function
. Best of all, the original harness wasn't cut up and can be reverted if I want to eventually go back to stock.