Mercedes B Klasse AC and Temperature Sensor Issue

It sounds like a sensor malfunction affecting your HVAC system. While a defective temperature sensor is possible, explore all related components before assuming a faulty air conditioning control unit. The error message and non-functional AC point towards a cooling system issue. When you say ‘temperature sensor heat exchanger’, can you identify which sensor is indicated in the diagnostic report? Knowing the precise sensor will narrow down potential causes. The temperature gauge may not reflect the issue depending on which sensor is at fault. Can you provide the exact error code? Sensor calibration is unlikely to be the primary cause, as sensors typically fail outright. However, problems in the wiring harness or connectors to the sensor could lead to similar symptoms. Check the wiring. This could stop your AC from working as the system relies on accurate temperature readings.

The error code is P0500. Should I check the wiring harness and connectors before assuming it's the air conditioning control unit?

The P0500 code typically refers to a Vehicle Speed Sensor malfunction, which seems unrelated to the temperature sensor and HVAC issues. This discrepancy suggests either a misdiagnosis or potentially multiple issues. It is unlikely the root cause of the error and more likely tangentially related. Given the diagnostic information and the symptoms regarding your AC and temperature-related error messages, it would be best to have a qualified technician thoroughly inspect the cooling system, HVAC system, and related sensors. While checking the wiring and connectors is a good measure, it cannot completely replace a professional inspection. The estimated repair cost might be justified depending on the extent of the damage and labor involved. In complex systems like the Mercedes B Klasse, a proper diagnosis and repair are crucial to ensure optimal performance and prevent further issues. It's possibly best to avoid DIY fixes in this case.

I brought the car to a workshop, and it turned out to be a defective temperature sensor, as you suspected. After replacing it, the air conditioning system now works, and the error message is gone. It cost 980€ - exactly as predicted.