Temperature / Climate Control Issues

[Filmpros]

The Temperature / Climate Control slider on my 1997 Lexus LX-450 does not work properly. It functions more like an on-off switch. I get AC from 64 Degrees or below and it blasts hot air from 65 degrees and above. Is this typical or is there something wrong? Any ideas on what may be causing this if it is not operating properly?

 

[firetruck41]

Not normal. I would guess there is a sensor on the fritz, but I've no real experience messin' with the HVAC.

 

[96r50]

If this problem occurs on the auto setting I'd suspect the inside temperature sensor mounted behind the little grill to the left of the temperature slider. I believe you can clean the sensor just using compressed air and an old toothbrush. That's all I know about the auto system though!

One thing I would suggest is looking at the water control valve and making sure that it is adjusted properly. No tools required and takes all of a minute. There is a good thread about it here. After removing my rear heater plumbing last week I realized I must have bumped mine because the A/C wasn't as cold as it was before. Sure enough, I checked it out and adjusted it and presto, ice cold A/C once again!

HTH!

 

[KurtKuhn]

Filmpros, have you been through a stereo installation lately? Failing to hook up of all the bits upon reassembly of the dash in that area may cause this behavior.

Talked about here.

HTH

-KK

 

[corsair23]

99% chance that is the issue

Ask me how I know or just read the link from Kurt

 

[Filmpros]

Yes, as a matter of fact I did just have a Stereo install done ... interesting. I will have to get this checked out. Much appreciated. You guys are always helpful and it is greatly appreciated...

 

[landtank]

what is the ambient temperature? If it's say 60* out and you turn it to 65* then yes it will blow hot air.

There isn't enough info here for anyone to determine if there is a problem.

 

[nat88toy]

every thing is hooked up properly i can a sure you these units were the precursor to what is now "climate control" they are finakie at best there is just not a lot of brains with this thing compared to today's standards
anything above 65* is a warm tep at least were I hail from

 

[Filmpros]

OK...maybe this info will help?



1997 Lexus LX-450

115,000 Miles

Many, many, many Recent Modifications



70 Degrees outside temperature

Climate control slider set to 63 degrees Fahrenheit

Blows cold air … and I mean cold … ice cold



70 Degrees outside temperature

Climate control slider set to 64 degrees Fahrenheit

Blows hot air .. . and I mean hot … not warm …. hot.



I cannot get anything in between. It is pure hot or pure cold. Never warn or in between. Is that enough info to determine if this is working properly? I would hope it works better that this as it is useless the way it is. There is no control over the temperature at all. It is like an On / Off switch for Cold / Hot. Could it be a sensor of some sort or something wrong with the way it is mixing Cold / Hot air to achieve proper temperature in the vehicle?

 

[landtank]

My first guess would be that the slide control itself has a problem.

I don't know for sure but they are usually a wound resistor. As you slide the knob along it the resistance changes giving the controller a varied signal. Sometimes dirt or other type of failure can cause a dead spot or shift in the resistance and give a false signal.

You might have seen this sort of thing on volume knobs where as you turn up the volume it gets louder and then suddenly shuts off or goes real static. Same thing as what I'm talking about.

Do some searching on this and you'll find plenty of distaste for this system as far as controlling the air temps.

 

[KurtKuhn]

I cannot get anything in between. It is pure hot or pure cold. Never warm or in between. It is like an On / Off switch for Cold / Hot.

I had the exact same issue. The solution that worked for me was to remove the face plate and re-connect the white pick up tube to the back of the face plate (IIRC it is likely the tube that pulls in cabin air for a temp measurement).

Also, IIRC others have had success in blowing canned air (like the air used to dust off circuit boards) to clean the sensor associated in-line with this white pick up tube.

A couple of years ago when my LX was new to me, I drove from WV to DE with this binary climate control condition in the middle of winter. It was about to drive me crazy. Since then (and after the fix outlined above), I have had no issues with the climate control system. IMHO it works well.

Disclaimer: This fix is over two years old in my brain, and there may have been other bits that I had to reconnect. I do, however, distinctly remember the white pick up tube being disconnected.

HTH

-KK

 

[corsair23]

I'm with Kurt...

In my 40th 80 with auto climate control it was doing exactly the same thing...either full cold or full hot, NOTHING in between...

Read the thread linked to above by Kurt, then spend the 10 mins max to pop off the face plate and look for something that is not connected.

 

[Filmpros]

Thanks..I will take a look at this...much appreciated...!!!

 

[Filmpros]

Tried switching to "Manual" on the back of the unit. Same issue.

I will try using compressed air to clean out the temp sensor.

May also try tuner cleaner to see if it helps the slider control.

If none of that works, I am looking for the following part if anyone has a source for one used.

Toyota Heater Control & Accessory Assembly Toyota Part #: 55900-60020.

 

[Filmpros]

OK ... I did everything folks recommended and I read in every post and the AC / Heat still does not work properly.

Things I tried:

* Checked to make sure Temp Sensor Hose was Connected
* Checked to make sure all connections were secure
* Switched from Auto to Manual
* Cleaned Temp Sensor Intake with Compressed Air
* Cleaned Slider with Tuner Cleaner

The only thing I have not tried, because I cannot get behind the dash at the moment, is to check to see if anyone connected anything to the "blue" wire someone mentioned that has something to do with the heater control.

Are there any other ideas? I am at a loss and this is driving me crazy trying to figure out the issue.

 

[corsair23]

Sorry man...Thought for SURE it would have been as simple as reconnecting the plug. Got to ask, you verified everything was plugged in? For me IIRC it was a little white plug, not the white "hose" - Just making sure a connector didn't get pushed down out of the way and is hiding.

 

[Filmpros]

I did not see a white wire but I will look again. For sure there was a white hose. It used to work fine, but just stopped working.

 

[Dave 2000]

OK ... I did everything folks recommended and I read in every post and the AC / Heat still does not work properly.

Things I tried:

* Checked to make sure Temp Sensor Hose was Connected
* Checked to make sure all connections were secure
* Switched from Auto to Manual
* Cleaned Temp Sensor Intake with Compressed Air
* Cleaned Slider with Tuner Cleaner

The only thing I have not tried, because I cannot get behind the dash at the moment, is to check to see if anyone connected anything to the "blue" wire someone mentioned that has something to do with the heater control.

Are there any other ideas? I am at a loss and this is driving me crazy trying to figure out the issue.

Did you check the water flow slider on the heater hose under the bonnet close to centre bulkhead? I know it is mentioned but it was not in you 'done' list.

regards

Dave

 

[corsair23]

I did not see a white wire but I will look again. For sure there was a white hose. It used to work fine, but just stopped working.

Rich,

It has been a couple years so my memory might be faulty but IIRC there are two main (bigger) connectors on the back of the HVAC unit about in the middle. Then to the DS of the HVAC unit there is the white hose and to the PS of that hose was the little connector (maybe a two pin?) that connects to the back at the level of the temperature slider. I'm thinking it was a white/cream colored small rectangular connector...

Good luck in figuring out whatever it is that is causing the issue

 

[Pano Anthos]

OK...maybe this info will help?



1997 Lexus LX-450

115,000 Miles

Many, many, many Recent Modifications



70 Degrees outside temperature

Climate control slider set to 63 degrees Fahrenheit

Blows cold air … and I mean cold … ice cold



70 Degrees outside temperature

Climate control slider set to 64 degrees Fahrenheit

Blows hot air .. . and I mean hot … not warm …. hot.



I cannot get anything in between. It is pure hot or pure cold. Never warn or in between. Is that enough info to determine if this is working properly? I would hope it works better that this as it is useless the way it is. There is no control over the temperature at all. It is like an On / Off switch for Cold / Hot. Could it be a sensor of some sort or something wrong with the way it is mixing Cold / Hot air to achieve proper temperature in the vehicle?

I realize this is an old post, but did you ever resolve this?