AC climate control has a mind of its own (1 Viewer)

[Tinkertoy]

Boys I need your help. I have a 97 LX450. The AC is charged. It will blow cold. (When it wants to). So we have the climate control unit and many times it’s on and then the auto light changes and the recirculate will shift to circulate and then it will either shift to your feet or what ever and blow Lava hot air out.

So is this the module or possibly the AC amplifier? Sorry if there are threads on this. I haven’t found any.

 

[brockdeck]

Do you have a 40th edition with automatic climate control? You should have two amplifier s if so, and usually the auto amplifier becomes problematic on these trucks if you’ve ever had a windshield leak.

If not, start with the simple stuff. FSM has great tools to diagnose the AC system. If your climate control unit is all funky, there is likely an issue with it.

If you need a new one, I am sure @Deathvalleypaul would be able to sell you one and ship.

 

[retlaw]

If the temp slider is moved from min to max you would expect it to operate that way.....perhaps a bad connection in the slider resistor? As mentioned the Auto AC amp controls this and should be examined for water intrusion and corrosion. There are threads on that.
What do you mean "the auto light changes"? On mine it is green when in auto mode and changes to amber when you over-ride the system.

 

[Comet]

Check that the white tubes running to the auto detect thermostat (not sure on name) on the dash is connected. I believe it is similar to my 100 series auto temp. We had issues with temperature fluctuations and I believe that corrected the issue.

 

[rolliges]

White tube connected AND free of debris.

 

[Tinkertoy]

Do you have a 40th edition with automatic climate control? You should have two amplifier s if so, and usually the auto amplifier becomes problematic on these trucks if you’ve ever had a windshield leak.

If not, start with the simple stuff. FSM has great tools to diagnose the AC system. If your climate control unit is all funky, there is likely an issue with it.

If you need a new one, I am sure @Deathvalleypaul would be able to sell you one and ship.

Do you have a 40th edition with automatic climate control? You should have two amplifier s if so, and usually the auto amplifier becomes problematic on these trucks if you’ve ever had a windshield leak.

If not, start with the simple stuff. FSM has great tools to diagnose the AC system. If your climate control unit is all funky, there is likely an issue with it.

If you need a new one, I am sure @Deathvalleypaul would be able to sell you one and ship.

Thanks. No i have the Lexus version. As for window leak. I am not sure I’ve only had the truck a few months. The PO had it since 2004.
It seems odd that the AC Amplifier would change different buttons in the module. Or is that the symptom?

 

[retlaw]

The AC AUTOMATIC amplifier is what changes the settings automatically. This is the brain for the auto AC system. Its the white box above drivers knee that can fill with water from a leaky windshield.
It works with the AC SYSTEM amplifier (behind center dash) to control the air mix servo motor.
Then theres the plain old AC amplifier behind the glove box...I dont fully understand how all of these interact. This one seems to control some relays that work with the AC.

 

[Tinkertoy]

The AC AUTOMATIC amplifier is what changes the settings automatically. This is the brain for the auto AC system. Its the white box above drivers knee that can fill with water from a leaky windshield.
It works with the AC SYSTEM amplifier (behind center dash) to control the air mix servo motor.
Then theres the plain old AC amplifier behind the glove box...I dont fully understand how all of these interact. This one seems to control some relays that work with the AC.

So far that is what I have gathered as well. I also just looked up front and it seems my HCV may be stuck too. So maybe the system is trying to compensate? Who knows. I guess I need to figure out the HCV 1st now. No matter where I set the Temp it looks to be stuck open. So once the car is warm you get no cold air.

 

[retlaw]

I think the air mix servo controls the HCV.

The PO of my LX had left the AC system amp unplugged and I had no control on the HCV. It was behind the radio IIRC.