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2019 Lexus GS — a/C is cold on the highway but warm at stoplights

ProjectWrench614Community StarterMay 9, 20262019 Lexus GS 350Brooklyn
2019 Lexus GS 350, about 69,500 miles. The A/C works well with road speed but gets noticeably warmer at long lights, then cools again almost immediately once moving. Does that point more toward airflow/fan behavior than refrigerant level?
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4 replies

WrenchDriverCommunity StarterCommunity StarterMay 10, 2026permalink
I'd want a measurement, not a hunch. Move a coil or plug on the 2019 Lexus GS if it's cylinder-specific and see whether the code follows. Save the big job until that test fails. If they can't show the line item, I assume it's hiding. I'll poke at it this weekend.
BatteryLearner102Community StarterCommunity StarterMay 10, 2026permalink
This is usually cheaper to test than to guess. Move a coil or plug on the 2019 Lexus GS if it's cylinder-specific and see whether the code follows. Save the big job until that test fails. If they can't show the line item, I assume it's hiding. A day of patience here is cheaper than a wrong part. Happens in gear, not in park, for what that's worth.
WrenchDriverCommunity StarterCommunity StarterMay 10, 2026permalink
That's a good start, but I wouldn't stop there. A pressure test beats staring at a dry driveway if the 2019 Lexus GS is losing coolant with no puddle. Don't erase codes until someone who can help has seen them. Verbal 'we'll take care of it' is not a plan. I've seen both outcomes, which is why I'd test instead of assume. If that fails I'll eat the diagnostic fee.
TorqueWeekend186Community StarterCommunity StarterMay 10, 2026permalink
Log the conditions before you spend. A pressure test beats staring at a dry driveway if the 2019 Lexus GS is losing coolant with no puddle. That's the branch I'd chase this week. On “a/c is cold on the highway but,” that was the fork that mattered for me. Do that first. I'm keeping receipts and dates in one folder.
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