Climate Control Tune Up All Lexus/toyota

[Greavett]

Hi People,

Was driving today in the heat of a Queensland summer, climate control happily purring away keeping the sweat from beading on my forehead.

I thought of an interesting little thing you can all do for your A/C systems to make them a little more reactive to your temperature setting in side the cabin.

It is usually forgotten and once you do this little job you will find your Climate Control will return to being a little more effecient in the co-efficiency between your set temperature and what the system actually believes is the temperature inside the cabin.

Usually your modern A/C system uses a couple of sensors to detect the temperature within the cabin, the sun light hitting the car and the internal temperature of the A/C system itself.

I've been in numerous cars that when the A/C is set to 25'c it's no where near enough to keep the car to a nice temperature, you end up running the A/C at 18-20'c just to get the temp you desire. Amongst a failing A/C system with low gas or other problems there is a simple job which every one can do to make your A/C more reactive to interior temperature vs selected temperature.

When you select say 25'c the Ecu for the A/C will determine the amount of sunshine (solar sensor) vs Temperature demand (you selecting the temp you want) and the current temp output from the evaporator. Please don't quote me on the sensors this is just a summary of a basic system to keep it simple.

However, over time, the one sensor which collects dust like no other is the in cabin temp sensor. It collects dust because it has a handy little fan behind it, to draw in cabin air over the sensor (resistor-i-think, similar to MAF sensor).

The effect of this collective build up of dust and fur is that when you dial in your A/C to 25'c, your system will try to read the temp of the cabin air though the crusty dust which surrounds the sensor. Now those of you that have had Air Flow sensor problems due to dirt/oil on the resistor will understand that it does definitely effect the acuracy of the sensor.

Some of you through cleaning may have already come across the little sucker behind the dash, most I would expect would not know what it is.

With out pictures I will endevour to explain how to find the sensor on your A/C so that you can remove it, clean the fan and sensor so that your A/C system will get it's Climate Control nervous system back!!

They are usually located on the drivers side dash panel. Normally around the steering column area below the binnacle (Speedo Cluster).

They are usually inserted behind a small removable panel, which looks similar to an empty switch panel, except that it will have a number of horizontal vent holes. In size, approximately 5 cent piece, but the panel in which it sits can be quite a bit larger.

Gently prize the panel off, being careful not to damage either the wiring harness or the sensor/fan assembly.

Behind the vent I will almost put money on that all of you will find some level of filthyness!!!

Very carefully using cotton wool, or an ear bud, and some very gently electric cleaner such as Iso butamol (i think that's what its called) Dick Smiths sell it for PC guys, clean the surface of the sensor and the fan. Turn on your igntion and check that with the A/C on and running the fan does in fact work, and if it does put it back in your dash.

You will notice that your A/C Climate control is able to respond quicker to your temp commands and will maintain the correct level of cooling better without the sometimes large variation between cold and icy cold.

Give it a try.......I bet you all find fluff!!!!

Let me know how you go!?

Thanks for reading

Simon :)

[The Marque]

Hi Simon

Thanks for your informative post. I have a 92 LS400, everything works however I would like to check the climate control sensor as you suggested. However I just want to confirm the sensor location. I have a small 25mm square vent which is 30mm below the parking brake lever. The vent has narrow horizontal openings.

I have tred to remove this vent carefully with a screwdriver but have not managed to remove it so far. Please confirm this is the right vent and any tips on removal.

Cheers

Ric

[Greavett]

Hey Ric,

From memory, the cover is screwed in from behind the panel so don't pry it too hard. You will have to remove the ignition key surround (just pulls away) remove the coin tray, think there is a bolt behind it, another behind the handbrake lever, just pull the lever to gain access.

Then I believe there are two more bolts at either lower end of the panel. Gently lift the panel out and down. There will probably not be a fan on your model as there was none on my 95. Instead it uses a draft feed from the heater box to draw the air over the resistor.

Just pull of the rubber hose for that, disconnect the wiring and give it a bit of a gentle clean, re-fit in the reverse order. The fuel flap and bonnet release cables can be left on the panel, and just work the panel to the postion you need to get at the sensor.

Hope this helps

Simon

[Subby]

Simon,

I have an IS250 - 2007 - and the only thing that sort of matches your description of the location of the sensor is some vent slots on a large panel on the left side under the steering wheel.

There doesn't appear to be any easy way to remove the panel. Any suggestions would be helpful.

Thanks

Subhash

[Greavett]

Hey Subby,

There will be some hidden bolts/screws behind the panels, and if you can't see any at all after an extensive look, you may find that they are retained by wedge type fastners common to Toyota and Lexus.

The lower panel near your knees is generally the easiest panel to remove in the car as it's used for main access to the ignition harness etc. I'm sorry I can't be more specific but maybe some IS owners can shed some more light on it for you.

Thanks

Simon

[Subby]

Thanks, Simon - and please excuse the late reply.

If it's OK with you, I'll post this link on the IS250 forum and hopefully get some help from more experienced members in getting to the sensor.

Regards

Subhash

[Greavett]

No problems!

Thanks

Simon

[steve2006]

The sensor panel does not come off from the front, an easy way to clean it is to buy a can of compressed air and blast it through the slits in the cover.

[Subby]

• Thanks for that suggestion, Steve - will give it a go
  

[Subby]

_{Thanks for that suggestion, Steve - worked like a charm !!!}