This is a supplemental complaint to add more detail to a prior submission. I am the original owner of a 2021 Toyota Highlander with 10,000 miles at the time of the issue worsening to the point that I finally broke down and was forced to pay the Toyota dealership’s hefty diagnostic fee. The air conditioning system has failed due to a refrigerant leak in the rear A/C lines, specifically near the exhaust area under the vehicle. The dealership diagnosed the issue and quoted me over $3,000 to replace aœall necessary components in the rear.a They offered no coverage or goodwill repair despite the vehicleas age and mileage. Upon researching the issue for longer than a year at this point, I discovered far too many similar complaints from other Highlander owners (years 2019a“2021) describing identical failures a” typically rear A/C lines corroding, cracking, or leaking prematurely. In some cases, customers were told Toyota is aware of the issue but not issuing a TSB or recall. In other cases, dealers said no permanent fix exists. These repairs are prohibitively expensive and, in some reports, recurring due to poor line placement or dissimilar metal corrosion near heat sources. This significantly impacts safety in several ways: Impaired Visibility: The AC system is integral to effective defogging and defrosting of the windshield, especially in humid or cold conditions. Without it, visibility is severely compromised, increasing the risk of an accident. Driver Impairment: In extreme temperatures, lack of climate control can lead to driver fatigue, distraction, and reduced concentration, posing an indirect safety risk. I am reporting it to request NHTSA monitor the trend. This seems to reflect a possible engineering or design flaw, and the number of similar owner reports suggests it may warrant further review by Toyota and NHTSA. Customers should not be facing multi-thousand-dollar repairs on near-new vehicles with basic systems failing. Thank you for tracking this issue.