RVAHoo

The HVAC gets smelly if left on recirculate all the time. I have to switch it to outside air after every startup. The loaner I had did the same thing. Any advice on how to get the system to retain settings? Read the manual, but no help.

dibl

I would put my attention on the source of the odor -- automobile A/C has always worked best when set to recirculate, rather than trying to cool the already-hot outside air. Cabin air filter change might help, and the heat exchanger might have a little buildup of crud that needs cleaned off. 2 cents worth.

AndrewTO

If the A/C is turned on, it automatically defaults to recirculate. There isn't a way to override this, it's just how it's designed.

The smell is likely coming from mold or bacteria build-up in the system, and is common with Lexus/Toyota A/C systems. Switching it to outside air eliminates most of the smell from personal experience, though, you may also want to turn off the A/C a few minutes before you arrive at your destination to dry out the system.

blayze1983

I've actually never used the outside air because I do mostly city driving and with all the garbage trucks and construction around I wouldn't want that air getting into the car (and it's summer so A/C on).

Is it a good idea to change it to outside air every now/then? Is there any benefit? Would you do it on the highway? I don't leave the city much so not a lot of country road driving for me where there's fresh air!

dibl

As @AndrewTO mentioned, a side effect of the refrigeration process is pulling water out of the moist summer air, and the water condenses on the heat exchanger. The condensed water is supposed to drain out of the system -- that's the pool of water you see under a recently parked or idling car on a summer day. But the heat exchanger doesn't dry out completely, unless you do something like @AndrewTO suggested, and as a result there tends to be a gradual accumulation of microorganisms that can live or die and rot in a tiny bit of water. And then it smells bad.

blayze1983

Gotcha - so essentially what you're saying is YES - do change it to outside air every now and then. Will do that today!

AndrewTO

Alternatively, you can clean the HVAC system after the fact by spraying Lysol into the exterior vents located underneath the windshield to clean the system.

Though, I prefer preventative maintenance rather than reactive maintenance

Tarkus

You will also notice that in winter your windows will fog up if AC is off and you have re-circulate on. This is because of the humidity in your breath. It has no where to go. You keep breathing the same stale air. Turn off re-circulate and you introduce outside air and the windows will not fog up.

IMHO, re-circulate is only required when you want to,
Warm up or cool down quickly, then turn it off. Especially with a car full of people.
You pass a skunk or other noxious smells and want to isolate the cabin.

Cocal

Going on for 4 yrs and my RX350/2017 doesn't have any A/C smell, neither did my MB350 nor any of my other cars, so there must be some other factor, perhaps as others have said the evaporator has no time to dry.

dibl

AND turn OFF the A/C, so the heat exchanger can warm up and let the water evaporate off of it.

BMGS

iTrader: (1)

Go into the vehicle settings (not the HVAC settings) and select the option to turn off Auto A/C mode. I forget exactly what menu it's under but it's not the climate control settings.

Once that is turned off, go to the climate control settings screen and turn the A/C off. Then start the car and select the fresh air mode. The A/C should remain off per the climate control settings menu and you should not feel cold air, confirming the compressor is off. If you turn the car off in this setting, when you start it back up, the AC compressor will be off and it will retain the fresh air setting.

When you want to turn the ac on, from the physical recirculate button, select the middle Auto function. While looking at the climate control screen settings you will see the AC option is now activated. That's how you can turn in the compressor, and have a quick button control to turn off the compressor to intake fresh air, and have the system save that fresh air setting upon the next startup.

The downside is that when the ac is on, the setting will almost always be on recirculate. The upside is that its helped immensely to solve the mildew issue and keep it away after performing a couple evaporator cleanings through the intake vents. About 5 minutes before I park the car, I just hit the outside air switch to introduce warm air to the evaporator, which combined with the blower fan on high, will help to evacuate and prevent stagnant water from pooling on the evaporator

AST300

I believe the HVAC defaults to fresh/recirculate, at least in part, based on the difference between cabin air temperature and the temperature you have set. Recirculate mode should potentially result in a cooler cabin since no outside air is being introduced. So when the HVAC is asked to cool hot air, it will use recirc mode so it is cooling air that has already been cooled to some degree. And over time when the HVAC has caught up to the set temperature, I believe it will automatically switch to fresh. The heated/cooled seats seem to operate similarly if in Auto mode. If the heated/cooled seats are in Auto mode and the seats are either heating or cooling, adjusting the cabin temperature up or down will change the degree to which the seats are heating/cooling.

ravenuer

Exactly how I run my system.

lexnewbi

Mine AC automatically selects fresh or recirculate when in auto intake mode. It is mostly on fresh, but changes to recirculate when it needs to rapidly cool (like starting the car), its hotter outside than inside, or the sensor detects bad air outside (smells or smog). The smells or smog take a minute or so to be registered.

When the car it is turned off, it changes it to fresh.

From the manual:When the outside temperature exceeds 75°F (24°C) and the air conditioning system is on

• In order to reduce the air conditioning power consumption, the air conditioning system may switch to recirculated air mode automatically. This may also reduce fuel consumption.
• Recirculated air mode is selected as a default mode when the power switch is turned to ON mode.
• It is possible to switch to outside air mode at any time by pressing the outside/recirculated air mode button.
  

​​​​Automatic mode for air intake control

• In automatic mode, the system detects exhaust gas and other pollutants and automatically switches between outside air and recirculated air modes.
• When the dehumidification function is off, and the fan is operating, turning automatic mode on will activate the dehumidification function.

blayze1983

In theory automatic mode sounds good (other than those moments where you're stuck behind a dumpster in which case 1 min is an eternity). Do any of you guys practically use it? Is it effective?