Having an issue with my AC in which the cooling is varying constantly
even though I don't change the temperature settings. On a few occasions
the air just blew hot. After the car is turned off and sits for a while the AC
comes back full blast and then later heats up again. Compressor? or something
else. Any Ideas/

 

Isn't it a Lexus thing? Where it tries to heat the cabin to a certain temp and maintain it, rather than blowing a set temperature. It annoys me too in the winter when the heat stops blowing warm and blows cooler air, I have to turn up the heat to get it to blow warm air again

 

Don't aim the vents at your body and you won't feel the changes.
It adjusts what it puts out to maintain the cabin temperature where the sensors are, not where your skin is.
It is Climate Control, not basic Air-Con which just cools air and blows it at you.

 

What everyone said. I think it's just the way the climate control works. It adjusts to the temperature of the day. Not your ordinary AC system but maybe you need to check refrigerant

 

An automatic air conditioner system which provides enhanced air conditioner comfort according to the occupants’ senses has been newly adopted.

In the previous automatic air conditioner system, the ECU determined the required outlet air temperature and blower air volume in accordance with the calculation formula that has been obtained based on information received from the sensors.

However, because the senses of a person are rather complex, a given temperature is sensed differently, depending on the environment in which the person is situated. For example, a given amount of solar radiation can feel comfortably warm in a cold climate, or extremely uncomfortable in a hot climate.

Therefore, as a technique for effecting a higher level of control, a neural network* has been adopted in the automatic air conditioner system. With this technique, the data that has been fetched under varying environmental conditions is stored in the ECU, which effects control to provide enhanced air conditioner comfort.

*: Neural Network = Is capable of effecting complex control by artificially simulating the information processing method of the nervous system of living organisms in order to establish a complex input/output relationship that is similar to a human brain.

The neural network control consists of neurons in the input layer, intermediate layer, and output layer. The input layer neurons process the input data of the outside temperature, the amount of sunlight, and the room temperature based on the outputs of the switches and sensors, and output them to the intermediate layer neurons. Based on this data, the intermediate layer neurons adjust the strength of the links among the neurons. The sum of these is then calculated by the output layer neurons in the form of the required outlet temperature, solar correction, target airflow volume, and outlet mode control volume. Accordingly, the air conditioner ECU controls the servo motors and blower motors in accordance with the control volumes that have been calculated by the neural network control.

 

After researching this thoroughly, I think the evaporator core is the culprit. I am
taking the car to a Lexus Dealer asap. The car's windows fog up terribly when it's
raining and the defogger doesn't remove it like it normally would. This situation
goes deeper than what has been mentioned in the comments about my original
thread. I've got a bad feeling about this as my car has the ultra luxury package
and based on comments I've seen the dash has to be removed in order to replace
the evaporator. I'm probably looking at a big bill to have this repaired.

 

My 2004 had a similar random issue. It related to this sort of thing (hard to pin down) the radiator being topped off and the overflow having some coolant to add as well. And I guess those small black hoses can swell and cause these types of issues????

Like I say -very strange issue and related things, but if I added coolant to the overflow - AC stayed cold *shrugs*.