dashmer

Can anyone help explain how the a/c and climate control work together on this car? I have read the owners manual and it has not helped.

On another car I have owned that had auto climate control, you set the temp you want and the car does the rest. If it needs the a/c to get to the temp, it uses it with no further interaction from the driver. Just like the temperature control at home.

On the IS, while in auto on the climate control, if you set the temp lower (even significantly lower) than the cabin temp, it will crank the fan but will not turn on the a/c unless you either:
- press the auto button a second time; or
- press the a/c button

Also I noticed over the winter that the climate control would turn the a/c on at unexpected times for no clear reason (I used to think that it did it to either cycle the compressor or maybe it detected moisture in the cabin or windshield) but now I am not convinced that it is that sophisticated..

Anyone figure this out and can explain it to me? I feel stupid with this system. Thanks.

crazych42

OK I just posted something similar... I'm not sure what you mean by "press the auto button a second time..." By default if you press auto the a/c light should be on unless it was changed. When on auto mode the compressor (controlled by the "a/c" button) will cycle on and off during cold and warm/hot conditions to adjust the temp in the cabin, defog/defrost windows, etc. If you press auto and the a/c light does not come on automatically you or the dealer (can't recall if this is a dealer setting) can change the setting. Hope this helps.

dashmer

Thanks for the response. By pressing a second the auto button a second time, this is what I mean. Here is the scenario:
I get in the car and it is hot from the sun. I start it and the climate control is set to a cooler temp (say 20 C/70 F). The auto light is on, the a/c light is off and the fan starts speeding up until it is full blast. I do not feel the dry or cool air from the A/C. I wait 5 min and still no A/C. I can press the A/C button and the A/C light will turn on (and I get cool dry air) OR I can press the auto button again (it is already lit from when I started the car) and it will turn on the A/C light and I get cool and dry air. The next morning, temp is still set to (20C/70F) but the car is cold and I want some heat. When I start. the auto light will be on and so will the A/C light. I believe the A/C light will remain on indefinitely after that if I do not touch it again.

CJW

iTrader: (1)

There is a setting to turn AC on/off when using auto climate. Go into your car settings and it should be there.

dashmer

Thanks for the suggestion. I checked this setting and it is turned on. It would seem that the climate control will turn it on but never seems to turn it off again. The test I just ran was while the a/c was cooling, I ran the temp all the way up to the max...the result was the car turned the fan down to dead low, but did not turn off the a/c. It would seem that the car's ability to use the A/C is quite simplistic....unless mine is defective somehow..

mmims2000

I've owned a few different Lexus models and they all have worked the same way. Let's say you've totally taken control over the settings (i.e. you're in manual mode), and you've chosen your own fan speed, ventilation direction, etc. In this mode, the temperature controls only affect how hot/cold the air blowing out of the vents is. Now, if you were to press AUTO, this switches the system over to an automatic mode and allows it to take over control of all those functions, choosing what it believes is the best fan speed and ventilation direction to achieve the temperature you've set. On hot days it will ramp up the fan speed to max, and then wind down as the cabin cools. On cold days, it will ramp up the heat in a similar fashion, but it won't start ramping up until the engine block warms up (thus preventing it from just blowing cold air when you want heat).

When you press AUTO, the A/C compressor always defaults to ON (even if it's cold outside). You then have the option, if you want, to turn off the A/C compressor (by pressing the A/C button) while still keeping the system on AUTO and letting it control the other functions. You would typically do this in the winter when you don't want to run the A/C compressor and heat simultaneously. It seems counterintuitive that you have to tell the system that's what you want, but that's just the way it works. If you were to press AUTO again, it reverts to full automatic mode, which means it will turn the A/C compressor back on.

crazych42

OK I think I get what you're saying. It sounds like you normally drive with the auto button on and a/c button in the off position and are wondering why when in auto the a/c doesn't come on automatically to cool the cabin. Am I correct? I'm not sure what car does that but in all my previous cars I had to either cycle the auto off and on to get the a/c to turn the compressor on or hit the a/c button to turn it on. It would be nice to have a car that did it all on it's own, but then again there are times when I don't want the compressor running and would rather have the option to not run it.

dashmer

Thanks for the great explanation mmims. You have confirmed what I thought. A little disappointed that it is not a little more intelligent than that. My last car was a Hyundai Genesis Coupe and it was totally automatic. If it could not cool the cabin to the desired temp with just the outside air, it would kick in the a/c and then kick it back off when not needed. You could force the a/c to run when it was not called for, but I don't ever recall needing to do that.

dashmer

Yes you are correct.

jhs82

With auto om and A/C on, the compressor is used when needed. Not all the time.
With A/C off, the compressor never turns on.

dashmer

jhs,

Are you saying that even though the A/C light is on, the A/C system may not be in use? Or in other words, say if the system was heating and the A/C light is on, no air conditioning is occurring?

I know the compressor cycles on and off as needed when the air conditioner is operating, but you are receiving "conditioned air" the entire time. I think if the light is on, you are receiving "conditioned air" all the time (except for when the system is locked out due to environmental conditions). I would not bet my life on that, but that is what I think....

jhs82

You'll get air that has gone through the condenser, but not necessarily cooled air.
It helps a lot with condensation on the windshield.

Why would you not want that?

aTeAse

Using heater with AC ON, and AC off is providing different air to the cabin?

JKS613

Sorry this is going to be a little off topic but does anyone have problem with the AC not being cold/cool enough? My cAr does not feel like it's cold enough compare to other cars I've had.