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Air conditioning stopped cooling / no response to AC button

Q: How to fix Air conditioning stopped cooling / no response to AC button in BMW Seria 3 E90?

Absolute replacement of the evaporator (board down) with an improved element (from 2024, new coating supplier Mahle Behr). A typical plague (even 90% of early G generation cars). To confirm this 100% without removing the board, put UV into the LP port and use an inspection camera with a UV tube to enter through the cabin filter hole or the pulled out fan onto the core.

in BMW Seria 3 E90 (2017-2025)

Symptoms

Air conditioning does not turn on

DTC error codes

80120B (Compressor shutdown by vacuum)

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Technical diagnosis (Premium)

Recognized technical fault:

Auxiliary controller voltage instability detected

Technical analysis

Detailed analysis of HVAC controller operation parameters, CAN bus data readings, and diagnostic signal waveforms. Purchase PRO access or log in to read the full fault analysis.

Confirmed solution

Complete step-by-step repair procedure including module non-volatile memory reset, sensor calibration, and correct wiring routing. Unlock the full report to see the instruction.

Parts needed

Filters ferrite anti-interference / noise suppressor
Auxiliary starting battery (depending on cell status)

Workshop hacks

Important workshop tips for mechanics regarding bypasses without expensive control module replacement and manufacturer software service bulletins.

TSB / TPI service bulletins

TSB-24-HVAC-01TPI-2068943/2

A/C Technical Specifications

(G20)

Refrigerant: R1234yf Amount (g): 480-530g Oil: PAG YF ISO 46 Oil (ml): 120 - 150ml

(F30)

Refrigerant: R134a Amount (g): 520-570g Oil: PAG 46 Oil (ml): 120 - 150ml

See full specification

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