Climate Control Goes Cold After 30Mins

lordlen21 · January 10, 2016

Just wondered if anyone else has experienced the climate control going noticeably cooler after about 30 minutes. I normally have it set to 21 degrees but after a while it goes so cool I need to increase the temp to at least 23 to maintain the same temp.

CraigB · January 10, 2016

Hi,

Yes! I thought it was just me! The heating gets progressively colder the longer the journey

So I start a typical 2 hour journey with it set to 22, after two 2 hours I have it on 25 to maintain the temperature.

I haven't done anything about it yet. It will be interesting to see what people's repssonses are.

Cheers

Craig

PCM · January 11, 2016

I think I have to do the same too...

Generally find myself adding 1/2 a degree or so over time ...

DanD · January 11, 2016

Same issue with my RX450h and previously with a RX400h.

I can't help but wonder whether there is in fact no issue and whether the problem is that over time, the temperature within the car slowly increases (due to driver and passenger body temperature) and that it reaches a point where the system starts blowing in cold air to re-adjust the temperature to the selected one.

I think there is also a physiological/psychological element at work here:

I have a similar argument with my wife just about every night where she complains that she is feeling cold and turns the central heating up. Eventually, once the selected temperature + 1 degree has been reached, the system shuts down and the house gradually cools down. Wife complains she is getting cold... and turns the heating up further... and on it goes...

Once night it got so hot, I changed into my swimming shorts: that was enough to convince her to add/remove layers instead of playing with the central heating. :-)

Eire Lexus · January 11, 2016

Only way to be sure of the temp is to use the Auto function. If not using auto the fan can't adjust and will just dispense air from the vent at the set temperature without taking into account the in car temp. So using Auto function will regulate the fan and keep the temp at the desired level. Try it, it works well

lordlen21 · January 11, 2016

Thanks for all the replies, it's interesting that I'm not the only one. It's not down to perception as the my wife as also noticed cold air being blown into the cabin after about 30mins which causes me to increase the setting a couple of degrees just to keep warm. My BMWs didn't have this feature - did have a lot of others that greater though - you just set to 21 degrees and the auto function kept the cabin at the same temp. The Lexus seems to want to wake you up after 30mins by dropping the temp by 2-3 degrees when on Auto.

Doesn't bother me too much as all cars have their quirks and the rest of the Lexus IS is such an improvement on my 2013 BMW 320i, that increasing the temp is not an issue.

BigChange · January 19, 2016

I'm trying to understand the difference/function of Auto and A/C (IS300h). Handbook no help. Normally I leave Auto on and then turn on A/C but next trip the Auto comes on as usual but not A/C. So I switch on again. I'm wondering if A/C only comes on automatically when the weather is warm. Both functions came on automatically a few weeks ago so maybe it is the cold ?. Or maybe I'm doing something wrong. Any comments gratefully received.

On another tack, can anyone advise on how to adapt the HID lights for driving in France etc.

Thanks

Steve44 · January 19, 2016

If you have the economy settings set in the menus, then it will turn the ac on or off and the recirculation or external air switch depending on external temp and most eco setting when on auto.

You don't need to anything with the lights as they are flat symmetric beams apparently.

BigChange · January 19, 2016

Thanks Steve44. I'm not sure what you mean by "economy settings set in the menus". I just push the buttons but maybe it is necessary to access/program a menu? Sorry to be so dumb. More complicated than my BMW 320 !

Steve44 · January 19, 2016

Not sure which model you have, but if you have premium nav, go to menu/setup/car/Lexus customisations and check the climate settings. Other infotainment versions will be similar menu.

easyasqwerty · April 20, 2016

Same here. Over a year of battling this problem together with local dealer and I'm so dissapointed in Lexus leaving dealer to sort problem. Now they both refuse to acknowledge this is a problem and say its normal but suggested I log whats happening while driving. Im made to feel this is my issue that im too sensitive to temperature.

"Can you use a separate temp gauge to actual prove that the temp is dropping off after time as we have not heard of this issue.
If the customer needs the car can he photo the settings and then the temp gauge to show us it is dropping below what is set. It might vary by 1=2 deg either way but that's about it.

Yesterday indication was 28 C after 3 hr drive (82F in old money) this is normal!? Dealer has changed all temp sensors and ECU. I think problem began after software update about Feb 2015.

crispian · April 20, 2016

On 18/01/2016 at 7:21 PM, BigChange said:

I'm trying to understand the difference/function of Auto and A/C (IS300h). Handbook no help. Normally I leave Auto on and then turn on A/C but next trip the Auto comes on as usual but not A/C. So I switch on again. I'm wondering if A/C only comes on automatically when the weather is warm. Both functions came on automatically a few weeks ago so maybe it is the cold ?. Or maybe I'm doing something wrong. Any comments gratefully received.

On another tack, can anyone advise on how to adapt the HID lights for driving in France etc.

Thanks

No adjustment to your headlights needed for driving in France.

darrude · April 21, 2016

Mine does it too. Rarely changed the climate setting in my previous car (ie only really when in direct sunlight) this car, I adjust every journey. Once my wife shouted out mid journey "why has your car just blasted me in the face with cold air".

Does anyone else find the noise of the airflow annoying, can't decide if it is because the car is generally so quiet that it's more noticeable. But I drive lots of other cars and never been bothered by HVAC noise.

DJP · April 22, 2016

If the airflow is on the fast setting I can just about hear it. Set it to medium and no discernible sound at all.

Steve44 · April 23, 2016

Personally, I don't think the algorithm (PID loop for those in the industry) that Lexus uses to maintain a constant temp is very good. The blast of cold air in the face is noticeable as the auto setting switches which vents its using to output air, I guess in response to the sensor saying the cabin is too hot. Not sure if it has one or two cabin air temp sensors, I suspect 1, which is on the top of the dash and can get hot from direct sunlight shining through the window.

If you don't like the cold air blast, try not engaging the auto function, which only seems to swap around the air outlet profiles, or just turn off the centre air vents, or point them away from you.

I notice that the air vents don't have a diffuse function like my old car had, which spread the air out in all directions, rather than just directing in one.

ColinBarber · April 23, 2016

air temp sensor isn't on top of the dash, that is the sunlight sensor which is used to compensate for direct sunlight shining into the vehicle.

DanD · April 29, 2016

On ‎18‎/‎01‎/‎2016 at 7:21 PM, BigChange said:

I'm trying to understand the difference/function of Auto and A/C (IS300h). Handbook no help. Normally I leave Auto on and then turn on A/C but next trip the Auto comes on as usual but not A/C. So I switch on again. I'm wondering if A/C only comes on automatically when the weather is warm. Both functions came on automatically a few weeks ago so maybe it is the cold ?. Or maybe I'm doing something wrong. Any comments gratefully received.

On another tack, can anyone advise on how to adapt the HID lights for driving in France etc.

Thanks

The AUTO function means that the internal temperature will be automatically controlled, however this does not mean that the Air Con (A/C) compressor will be used: A common misconception is that A/C is used only to cool the car, which is incorrect as A/C is also used as a de-humidifier that helps keeping the windows clear of mist on damp and rainy days... even with the heating on.

On this basis, A/C may not switch on on a dry cold day, as there is no requirement for the system to either cool the car, or to remove unwanted humidity. The AUTO function will keep the car warm, but the A/C compressor will not switch on.

Hope this makes sense.

chris1601 · January 30, 2020

I know this is an old thread, but was there any fix for this? I also find that the cabin temperature gets slowly lower over time. I generally settle on 22c but if I start at that, I end up in a sauna for the first half an hour of my journey so I start at 20c then increase to compensate as the temperature in the cabin drops. Never had this on any of my previous german cars, nor the Toyota Auris I came from before the IS300h.

Casaubond · January 10

Hi, Lexux 300h IS owner here, and I was shocked to find out the same problem, The car is 69 reg 300h F , and the climate works perfectly for the first 30 minutes or so, then when the temperature in the cabin gets to the set degree lets say 21, the cold air start to be pumped through the vents.

No other previous cars did that? has any solution been found? do I need to contact the dealer?

wharfhouse · January 10

2 hours ago, Casaubond said:

Hi, Lexux 300h IS owner here, and I was shocked to find out the same problem, The car is 69 reg 300h F , and the climate works perfectly for the first 30 minutes or so, then when the temperature in the cabin gets to the set degree lets say 21, the cold air start to be pumped through the vents.

No other previous cars did that? has any solution been found? do I need to contact the dealer?

I have mine always set to auto - generally temperature of 20C in summer and 22C in winter. I do a lot of long journeys and never had a problem - the car maintains what I set it at for the whole journey and I finish with it feeling the same temperature as when I start after the cabin is up to heat). However I do notice that every so often on a long journey the car will for a few minutes circulate slightly cooler air - I thought that this might be some sort of process freshening the air in the car as it soon reverts back to what it was. I don't touch anything when this happens and the system then continues to maintain the set temperature after that.

Casaubond · January 10

1 hour ago, wharfhouse said:

I have mine always set to auto - generally temperature of 20C in summer and 22C in winter. I do a lot of long journeys and never had a problem - the car maintains what I set it at for the whole journey and I finish with it feeling the same temperature as when I start after the cabin is up to heat). However I do notice that every so often on a long journey the car will for a few minutes circulate slightly cooler air - I thought that this might be some sort of process freshening the air in the car as it soon reverts back to what it was. I don't touch anything when this happens and the system then continues to maintain the set temperature after that.

Thank you, wharfhouse.

Your answer suggests my car has a problem, possibly a software problem, as it works very well with plenty of nice heat when it starts and until the cabin temperature reaches the set climate temperature on the auto setting. In my case, once the cabin temperature is reached, active cold air- from outside is pumped into the car through the static vents especially (the ones used for demystifying). It is not for a few minutes only, it is most of the time cold air, and the temperature in the car is not dropping overall but the blow of cold air in the face is soooo annoying. If I raise the temperature lets say from 20 to 21 the air becomes hot again - so the system does work , not sure why is set to blow cold air once it reaches the set temperature

I hope it is a software issue rather than some expensive failure of a sensor or such

matt8 · January 10

There is a small sensor on the dashboard, that detects cabin temperature. As a first port of call, a little cleaning of that may help.

ColinBarber · January 10

Sounds like normal auto behaviour to me if the cabin temp isn’t dropping. Once up to temp the air goes cold (well ambient and might feel cold if you have had 30+ deg air directed at you whilst the cabin was getting up to temp) and is directed to the body and away from feet. Adjust the vents or use manual air position selection if auto isn’t working for you.

Casaubond · January 11

13 hours ago, ColinBarber said:

Sounds like normal auto behaviour to me if the cabin temp isn’t dropping. Once up to temp the air goes cold (well ambient and might feel cold if you have had 30+ deg air directed at you whilst the cabin was getting up to temp) and is directed to the body and away from feet. Adjust the vents or use manual air position selection if auto isn’t working for you.

Hi ColinBarber, possibly a Lexus quirk. No other car brand that I have travelled on actually blows cold air when the cabin temperature reaches its set point in cold climate - The usual observed behaviour is to reduce the blow of hot air to a minimum to maintain the temperature. I am messing with the fans to find an optimal position setting.

When I go for the next service with Lexus I will raise this issue with them

Thackeray · January 11

3 hours ago, Casaubond said:

I am messing with the fans to find an optimal position setting.

There was a thread a couple of years ago (I can't find it at the moment) where a new owner was reporting something similar. It turned out that this driver was trying to adjust the fans to a preferred setting. But the problem he/she had was that when you adjust the fans, their auto speed setting is also turned off. Everything else remains auto but the fans will continue at high speed if that's how they were set earlier.

With climate control set on Auto and the car starting from cold in cold weather, my experience is that there is initially little air coming out of the vents. This is because the air is still cold, even if it's being drawn from inside the car rather than the freezing air outside. But when the engine is warm enough to provide heat (maybe three or four minutes - maybe longer in cold weather) the fans start to speed up to provide warm air to the cabin, including from the face vents.

This continues until the cabin has reached the set temperature. The fans then slow down again and the face vents gradually switch to cooler air. So you then have warm air near your feet and cooler air towards your face.

But if you make any adjustment, the function you've adjusted will no longer be automatic until you reset the Auto button. I find this works fine. If yours is not doing this when climate control is on Auto and no adjustments have been made manually, then, as you say, there might be a software or sensor problem. Let us know how you get on.

Incidentally, here's the link to the earlier discussion, though this was mainly about demisting.