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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 A5 (F5)?

Replacing the evaporator with a new element. To remove the entire HVAC box from behind the dashboard, the body structure on A4 B9 models often requires complete removal of the vehicle's windshield in order to remove the dash frame and maintain mounting access.

in Audi A5 (F5) (2015-2023)

Symptoms

No cold air from vents

DTC error codes

Low refrigerant 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

kompresor Denso 6SAS14/SES14

Refrigerant: R134a Amount (g): 600g Oil: PAG PAG 46 lub PAO 68 Oil (ml): 110ml

A5 - Cabrio kompresor: Denso 6SEU14 + 7SEU17

Refrigerant: R134a Amount (g): 600g Oil: PAG PAO 68 lub PAG ISO 46 Oil (ml): 150ml

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 A5 (F5)

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