This may sound stupid but I would rather look foolish in front of you guys than the service manger...
On your GX's does the fan speed (especially here in the lovely Chicago winter) seem to "hunt" around a bit as the car is driven for the first 10-20 minutes? It seems like it goes to a pretty high speed and then drops to a bit lower speed and after a while it may go back to the higher speed - all without changing the driver/passenger temp. The fan or air flow also seems "noiser" than my old explorer - kind of odd for a "luxury" vehicle in my opinion. The other weird thing is that if you are in the climate screen the fan may show the "medium" setting on auto, but if you manually press the same speed button the fan actually slows down a bit and seems quieter - almost as if the "auto" function is more of a variable speed fan control and the 5 speed buttons are simply preset speeds which then the computer illuminates the one closest to the variable speed it's running at.
Sorry for the ramble - I'm just wondering if this is normal.

 

Everything's fine! The auto climate control is very advanced. I notice also that it "hunts" for the right fan speed. For example, in the cold weather, if you start it up and put it to max hot, it may go to med, then back down 1 because when it goes up to medium, the amount of air passing through makes the air cooler than it should be so it lowers the fan speed back down after the temp sensors pick it up. I also did notice that there are a few different variable settings for the buttons you see on the screen. I was once watching the climate screen and I heard the fans go faster but the level on the screen didn't change.

It's just very complex, but everything's fine/normal.

 

Sorry to hijack this thread, but I may have a problem with my climate control that is different than MarkP's - and this thread reminded me about it. My truck is 3 months old and whenever I hit the 'auto' button, even when the interior temp is colder than the outside, the A/C always comes on - I have to manually hit the A/C button off. Does this happen to everyone else or do I need to get this fixed? Or is there a setting I am not aware of?

 

I believe this is normal - the system uses the AC to dehumidify as well as cool - it's on in my truck even here in 20 degree temps with the heat blowing.

 

A/C doesn't just keep air cool, it is good for heat also! Most manufacturers didn't know this or just don't care, but your system is working fine.

 

yup, that's what the auto a/c does when you press the "suto" button. BUT it depends on the temps, it can either cool the car, or warm it up when you press the "auto" button. also, if it's a really cold day and you have your "auto a/c" on, the system takes about 2-5 minutes before the heater turns on. I noticed all of these back in my rx300!

 

no no, it's ok. that's why we have forums like these to talk to instead of dealing with those service reps whom some are nice (the case for me) and some not really great. sometimes we may even know more than the service reps (i'm not saying i do but some of us do)

 

AC vastly improves defogging windows w/ the hot setting. And i too notice the AC always com- ing on in auto. I would like for the system to "respect" when I choose to turn it off and not come back on until I tell it too. But, it seems that it comes on when you hit auto. I guess thats the default.

 

Correct. If the A/C could not come on automatically, your windows would become fogged up either from winter weather conditions or from interior humidity vs exterior humidity (i.e. cold breath)

The Automatic Climate Control system is very advanced. But it's not perfect. They either need additional sensors or updated software to control it. In the dead of winter (below 30 degrees), turn into the sun and the fan will increase speed with cold air pouring out. So much so, I generally need to increase the temperature by at least 4 degrees.

The designers must feel if the sun is hitting the dashboard, the air temperature in the vehicle must be warm enough to start cooling. While I do agree sunlight can affect conditions, the Climate Control's reaction is way to agressive.

 

I'm late to this thread and hopefully your question is answered Marcp
No need to be bashful here . We're all here to help.

 

There were a number of posts on this 1+ yrs ago. I researched with service rep; long and short is computer trying to do too much using sun sensor et al.

Best way to operate it is to take it OUT of auto. Leave AC on always. I set fan speed at Low or Med, then just set the desired temp. I sometimes change the ducting to give windscreen extra when needed, or direct it all towards teh cold feet. This solves the cold air blasting in our facae when in Auto.

Maybe they'll get improved software, it hardly suits a 50K motor to have such a poor automatic HVAC.

DON

 

Thanks for the input Don - but if Lexus told you the best way is to not use AUTO I find that completely unacceptable - I'm bringing mine in for the 1000 mile service check and will talk to them about this issue and see what they say...

 

I don't think Don is indicating that Lexus told him this. I agree there is a problem. Automatic Climate Control temperature settings should not be tweaked during the season. Only when season changes I believe there should be a slight adjustment (a few degrees for heat to cold swing).

I don't like the turn off Auto idea. I just always keep the upper vents faced away from me, and if it gets bad (cold air blowing during winter) I'll increase the temperature a few degrees until it calms down.

BTW, this is not an exclusive issue to the GX, my dad is new to Lexus and he complained about the RX doing the same thing.

 

You can have the "AUTO" on with A/C off. Just go to "climate" turn A/C off. When you restart the engine, AUTO is on but A/C is off. I keep it this way during the winter. Hit AUTO again, and A/C will turn back on though.

 

Correct, Lexus did not tell me to turn AUTO off, they simply explained how the computer software is too sophisticated. It combines cabin temp, inlet air temp and humidity, sunlight etc in the algorithm that drvies the HVAC settings. They cannot do anything to stop it blowing cold air in your face all the time, it's the overactive computer trying to anticipate.

When you leave it in manual, you disable these fancy anticipating features, and it simply tries to contorl cabin temp to achieve your setpoint, and comfortable humidity. It is operating in semi-automatic mode, it will still control temp and humidity without annoying the occupants.

DO NOT turn off AC, as others have noted that dries out the damp winter or summer air to defog the windows.

I was excised about this when we got the car a year ago, today it's below the radar, the HVAC is satisfactory if not elegant in semi-auto mode. I'm more concerned these days about the clunk --is it getting worse? Or, that the wife or I will forget and pull the rear door handle while the otehr is electrically unlocking --and jam the mechanism. We live 9 hours drive from a Lexus dealer!

DON