What are the symptoms of Unusual noise and metallic grinding when A/C is on in BMW Seria 5 (E34)?

No cold air from vents. Unusual noises when A/C is turned on. Frost or ice on pipes under the hood

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Unusual noise and metallic grinding when A/C is on

Q: How to fix Unusual noise and metallic grinding when A/C is on in BMW Seria 5 (E34)?

1) R12→R134a CONVERSION (if the car has not been converted yet): Replacement of the oil in the system, all gaskets with dedicated ones for R134a and the dryer. 2) CLUTCH: If the compressor does not rotate when the A/C is turned on, check the voltage at the clutch coil. Note plug compatibility - older E34s have a 1-pin or 3-pin connector, adapters are available. 3) COMPRESSOR: When replacing with a used one, check the compatibility of the electrical plugs. Never install without first flushing the system and replacing the dryer. All repairs require professional refrigerant extraction before disassembly. Clutch test without diagnostics: with the engine running and the air conditioning on, power the clutch coil directly from the battery - if it clicks and catches, the problem lies in the control system (pressure sensor, relay, fuse), not in the compressor itself.

in BMW Seria 5 (E34) (1988-1996)

Symptoms

No cold air from vents
Unusual noises when A/C is turned on
Frost or ice on pipes under the hood

DTC error codes

No codes (analog era)

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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

(G30)

Refrigerant: R1234yf Amount (g): 520-570g Oil: PAG YF ISO 46 Oil (ml): 130 - 160ml

(F10)

Refrigerant: R134a Amount (g): 600-650g Oil: PAG 46 Oil (ml): 150 - 180ml

See full specification

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