jvillier

Have 2017 RX. Several occasions on highway after 1 hour or so where AC compressor shuts down (quits cooling) and fan speed reduces. Does not appear to show ECO mode anywhere. Get home, unpack car, restart and AC comes right back on. Discharge temp down to 40 degrees. Any reason why it would quit cooling? Does this have anything to do with S-mode?

JSracer

climate settings chosen or set to automatic ?? if automatic, it could be by design. if target temp, and cabin temp are matched.
when compressor shuts down, it will not run manual if you set the temp and fan speed ??
fan speed reduces in manual mode or automatic ??

"The Lexus S-Flow System uses sensors to detect if the front passenger seat is occupied and if it isn't, the system shuts the vents so to efficiently deliver air only to the driver and not the unoccupied seat."

jvillier

generally when running manual. Cabin temp increases despite lowering temp setting, doesn’t matter in adjust fan speed to max, still not as fast when working correctly with compressor on. Changing S-flow setting back and forth doesn’t matter with two people in the car, although there may be a slight increase in fan speed with setting off. Turning AC off and waiting to turn back on doesn’t matter. CouLd blockage of rear vents matter if packed with cargo? AC still working fine in town with shorter drives. Did two trips in past month when this happened. Both trips AC worked fine on the way to destination, shut off on return trip after about an hour. May have been hotter outside temp in mid-high 90s.

QUOTE=JSracer;11338019]climate settings chosen or set tautomatic ?? if automatic, it could be by design. if target temp, and cabin temp are matched.
when compressor shuts down, it will not run manual if you set the temp and fan speed ??
fan speed reduces in manual mode or automatic ??

"The Lexus S-Flow System uses sensors to detect if the front passenger seat is occupied and if it isn't, the system shuts the vents so to efficiently deliver air only to the driver and not the unoccupied seat."[/QUOTE]

jvillier

Are there return air ducts somewhere in the rear on the floor? Wonder what would happen if the return ducts are blocked and the recirc is on.

JSracer

strange, high speed manual should be high speed.
recirc would pickup from the front,

check the cabin air filter ?? easy, behind the glove box.

mine is always set in auto, and comfortable. probably a handful of times I have changed air flow since I've owned it. I do very long trips in the car, and its comfortable. fan never seems to blast to maintain

golferjack

Your comment "AC still working fine in town with shorter drives. Did two trips in past month when this happened. Both trips AC worked fine on the way to destination, shut off on return trip after about an hour.", makes me think that the lines are icing up and so the warm air comes on until the lines thaw.

jimbosr1

Maybe low on refrigerant. have it checked out.

RollingBlu

My ‘16 450h AC does the same thing. It shuts down when you need it the most – when the system is working the hardest like a very hot day in heavy traffic or if the car idles too long. The system just blows warm air, the occupants sweat. At idle, the engine shuts off and there is no way that I’m aware of to force the engine to run.

Toyota looked at it – Coolant refrigerant level was fine but the car had posted a few reports of the shutdowns. They said it was a safety device (don’t recall what they called it) that is supposed to shut the AC down under stressed conditions. AC returns after the car sits unused for a while. Under normal circumstances, the AC works well.

ravenuer

The dealer only checked the coolant level when you complained about the AC? Seems like they could have checked the refrigerant in the AC system.

RollingBlu

My mistake. I meant to say "refrigerant". Post corrected.

Side note: I explained the problem, symptoms, resolution in great detail to Lexus service writer. He put 'AC blowing warm air' on the service ticket. The tech naturally checked the air temp and refrigerant and found they were OK and returned the car. I insisted on speaking directly with the tech. After that he plugged in his ODBII scanner he saw that the AC system had logged several shutdowns.

JSracer

definitely worth checking the ac charge,
(should have been my first suggestion, but I was thinking why the fan was slowing down... could be a distraction, and be a result if the fan is smart in manual mode vs a second condition)

jvillier

Discussed with former lead service tech today. This is a long-standing known problem with this RX generation. Was told Lexus and A/C manufacturer blame each other. In SE US, high humidity , high temps, long hway drives, A/C evaporator coil freezes up. Lexus engineers unable to figure out why or what the fix is. Cant reproduce problem in the shop. Still occurred with replacement of evap coil. A/C fine with in-town driving shorter duration. Only suggestion is to run higher temps (>70) when outside conditions exist. Dealer plans to send the issue back to Lexus tech engineers to see if any progress with a possible fix. Nice to know I'm not alone and dealer/Lexus well aware.

jvillier

Had system checked at dealer - refrigerant level fine. Case sent to Lexus. Response indicated no known fix. Freezeup occurs then system responds after thaw. Advice was to run to open air intermittently instead of constant recirculate.

jcg0324

Perhaps one of the temperature sensors is not performing correctly. Just a thought.

jvillier

Next time in I'll mention that to the service manager who worked this. Not sure how that would be checked, perhaps only just replaced?