What are the symptoms of Hissing from vents and slow loss of refrigerant in Porsche 911 (991/992)?

Frost or ice on pipes under the hood

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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 Porsche 911 (991/992)?

911 TSB 64 06 13: Evaporator temperature sensor replacement + pressure sensors update (4M0959603J). Cayenne/Panamera MLB: identical procedure to Audi Q7 - check the o-ring and G395 sensor (often the Schrader valve allows replacement without suction). Compressor: check the N280/ECV valve before replacing the entire compressor. Cayenne E3 and Panamera 2017+ are MLB Evo platform = identical to Audi A8/Q8. Audi parts often fit and are 30-60% cheaper. Always compare the part number before ordering a genuine Porsche.

in Porsche 911 (991/992) (2003-2025)

Symptoms

Frost or ice on pipes under the hood

DTC error codes

Evap temp sensor fault

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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

(997)

Refrigerant: R134a Amount (g): 850g Oil: ND8 PAO 68 lub PAG ISO 46 Oil (ml): 195ml

(996)

Refrigerant: R134a Amount (g): 900g Oil: PAG 46 PAO 68 lub PAG ISO 46 Oil (ml): 180 – 210ml

(993)

Refrigerant: R134a Amount (g): 840g Oil: ND8 PAO 68 lub PAG ISO 46 Oil (ml): 80 – 120ml

See full specification

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