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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 Toyota Highlander?

Dismantle the drain hose, mechanically remove the accumulated paraffin wax from the evaporator housing and implement the drain cleaning procedure in accordance with the official technical bulletin (T-SB).

in Toyota Highlander (2020-2022)

Symptoms

Musty mold odor from vents

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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

Standard

Refrigerant: R134a Amount (g): 820g Oil: ND8 PAO 68 AA1 lub PAG ISO 46 b.d. Ipsum Oil (ml): 1996 – 01ml

Standard

Refrigerant: R134a Amount (g): 750g Oil: ND8 PAO 68 AA1 lub PAG ISO 46 b.d. Oil (ml): b.d.ml

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Hissing from vents and slow loss of refrigerant

Symptoms

A/C Technical Specifications

Other problems in Highlander

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