What are the symptoms of Unusual noise and metallic grinding when A/C is on in Audi A4 B5?

Unusual noises when A/C is turned on

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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 Audi A4 B5?

Comprehensive SYSTEM FLUSHING. Replacement of the compressor, condenser, dryer, TXV valve. No mercy for old tubes. Simply replacing the compressor is a death sentence for a new compressor (it will die within a week due to old filings). If you see glitter-like filings on the throttling nozzle filter (or TXV), repair costs increase threefold.

in Audi A4 B5 (1997-2005)

Symptoms

Unusual noises when A/C is turned on

DTC error codes

Brak

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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

(B9)

Refrigerant: R1234yf Amount (g): 580g Oil: PAG ISO 46 YF Oil (ml): 110ml

(B9)

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

S4 / RS4 (B9) - Wersje z czynnikiem R134a (590g) oraz R1234yf (525g)

Refrigerant: R134a / R1234yf Amount (g): 525 / 590 ±15g Oil: ND-12 / SP-A2 / PAG46yf Oil (ml): 100 / 110ml

See full specification

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