Mercedes-Benz W211 Air Quality Sensor - Used Original Parts

Diagnosis and Common Symptoms

As the senior technician at M.S. Motor, I see these sensors fail quietly. The primary function of the Air Quality Sensor (AQS), designated as A32n1 in the wiring diagrams, is to detect exterior pollutants like NOx and CO. When high levels are detected, it signals the KLA/AAC (Automatic Air Conditioning) control unit to automatically close the fresh air flap and engage recirculation mode, protecting cabin occupants from traffic fumes.

A failure of this sensor will not trigger a check engine light. The failure is subtle, manifesting as a loss of a luxury convenience feature.

Common Symptoms:

• Automatic air recirculation mode no longer engages when behind other vehicles or in tunnels.
• Noticeable exhaust fumes and outside odours entering the cabin while the climate control is in "Auto".
• Manual operation of the recirculation button still works, but the system fails to manage it automatically.

Stored Fault Codes (retrieved with STAR/Xentry):

• B1265 - Communication with component A32n1 (Air quality sensor) has a malfunction.
• Faults indicating an open circuit, short circuit, or implausible signal from the sensor.

Introduction

Restore the intelligent climate system of your E-Class with a Genuine Mercedes-Benz Air Quality Sensor. Sourced from original vehicles, each unit is meticulously inspected and bench-tested by our technicians to ensure it responds accurately to simulated pollutant levels. This provides a cost-effective and reliable path to reinstating the full functionality and comfort of your vehicle's automatic air recirculation system.

Product Details

• Brand: Mercedes-Benz

• Model Compatibility: W211 E-Class, C219 CLS-Class

• Part Name: Air Quality Sensor (AQS) / Schadstoffsensor

• Condition: Genuine Used (Tested Working)

• Notes: This sensor is a critical input for the KLA/AAC control module. It is typically located in the fresh air intake plenum beneath the windscreen. A faulty sensor defaults the system to fresh-air mode, disabling automatic protection from outside pollutants.