What are the symptoms of Slow loss of refrigerant or A/C system leakage in Audi A3 (8L)?

No cold air from vents. Problem visible at standstill or in traffic

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Slow loss of refrigerant or A/C system leakage

Q: How to fix Slow loss of refrigerant or A/C system leakage in Audi A3 (8L)?

Replacing the sensor with a new, modified version (green dot on the housing, e.g. 4M0959603E, 4H0959126A, 4H0959126C) with a new O-ring. Replacement does NOT require sucking out the gas because there is a Schrader valve under the sensor. In case of a harness problem: cutting out the rotten wires in the chassis member and soldering new sections. The sensor can be replaced without sucking out the gas! The Schrader valve under the sensor protects the system. Saves the cost of operating the machine (~PLN 200-400). Green dot = corrected version.

in Audi A3 (8L) (2002-2023)

Symptoms

No cold air from vents
Problem visible at standstill or in traffic

DTC error codes

00819

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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

(8Y)

Refrigerant: R1234yf Amount (g): 450g Oil: PAG ISO 46 YF Oil (ml): 100ml

RS3 (8V / 8Y) - Platforma MQB (rynki poza UE mogą nadal posiadać R134a)

Refrigerant: R134a / R1234yf Amount (g): 450 - 525 ±25g Oil: ND-12 / PAG46yf Oil (ml): 110ml

e-tron (8V)

Refrigerant: R134a Amount (g): 500g Oil: G 052 535 M PAO 68 AA1 Oil (ml): 120ml

See full specification

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Slow loss of refrigerant or A/C system leakage

Symptoms

DTC error codes

A/C Technical Specifications

Other problems in A3 (8L)

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