What are the symptoms of Hissing from vents and slow loss of refrigerant in Audi Q7 (4M)?

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

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Hissing from vents and slow loss of refrigerant

Q: How to fix Hissing from vents and slow loss of refrigerant in Audi Q7 (4M)?

Full disassembly of the dashboard and replacement of the evaporator. In Q5 (FY) models, precise installation of the SR3 bracket (fuse box) is crucial - an error during installation causes subsequent leakage of rainwater into the cabin. The manufacturer has issued a U43 warranty extension (10 years/100,000 miles) for selected models. Before expensive disassembly, check the gas detector at the vents - if the signal is positive with 0 UV dye under the hood = 100% evaporator.

in Audi Q7 (4M) (2013-2025)

Symptoms

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

DTC error codes

G395 low pressure

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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

(4M) e-tron

Refrigerant: R134a Amount (g): 890g Oil: G 052 535 M2 PAO 68 AA1 Oil (ml): 290ml

(4M)

Refrigerant: R1234yf Amount (g): 600-650g Oil: PAG YF ISO 46 Oil (ml): 150 - 180ml

(4M) kompresor Denso 6SES14 + 6SAS14

Refrigerant: R134a Amount (g): 700g Oil: PAG PAO 68 lub PAG ISO 46 Oil (ml): 110ml

See full specification

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Hissing from vents and slow loss of refrigerant

Symptoms

DTC error codes

A/C Technical Specifications

Other problems in Q7 (4M)

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