What are the symptoms of Unusual noise and metallic grinding when A/C is on in Audi A6 (C4)?

Unusual noises when A/C is turned on. Hissing from vents. Slow loss of refrigerant

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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 A6 (C4)?

Cutting out the rotten section and welding a new section of the pipe (aluminum TIG welding) or replacing the entire hose. Prevention: when dismantling, use silicone grease under the clamps. Diagnosis: connect technical nitrogen to the system under pressure and check with an electronic detector at each tube mounting clamp - hissing = leakage.

in Audi A6 (C4) (1986-1998)

Symptoms

Unusual noises when A/C is turned on
Hissing from vents
Slow loss of refrigerant

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

(C8)

Refrigerant: R1234yf Amount (g): 500-550g Oil: PAG YF ISO 46 Oil (ml): 130 - 160ml

S6 (C8) - Najnowsza platforma C8 (4A)

Refrigerant: R1234yf Amount (g): 500 - 550g Oil: PAG46yf Oil (ml): 110 - 140ml

(4G/C7) kompresor Denso/Zexel

Refrigerant: R134a Amount (g): 570g Oil: PAG PAO 68 lub PAG ISO 46 Oil (ml): 120ml

See full specification

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Unusual noise and metallic grinding when A/C is on

Symptoms

DTC error codes

A/C Technical Specifications

Other problems in A6 (C4)

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