Well guys. I don't know what to tell you but Cinc04 was right.
Paul

 

So Dave solved his problem by cleaned the sensor for the AC which is under dash, by the right knee, not the auto light solar sensor. That makes sense.

I know the diagram indicates that solar sensor also feeds to the AC assembly, it still difficult for me to accept it has anything to do with the AC.

I did an experiment by putting the black tape over the solar sensor, my headlights were on and my AC still blew the cold air.

 

OK. Found the sensor under dash on drivers right side. My 2002 Electrical Wiring Diagram manual calls it the A/C Solar Sensor. It has a small grill in front to be able to draw air into the sensor through a tube connected on the back. So. Dave did call out the correct sensor. I made an incorrect assumption. Misunderstanding what he was talking about. I now know because I looked under the dash. I will clean it tomorrow since it probably hasn't been cleaned in 20 years. There are indeed two sensors that apparently have digital data signals to the ECU's. The A/C Solar Sensor on drivers side and the "Autimatic Light Control Sensor. Dave. Thanks for starting this thread. I think we all learned something new. 😁👍

Paul

 

A/C ambient air temp sensor.



When putting the kick panel back together, don't forget to hook up the air sample hose on back.
Tools required - Phillips Screwdriver, 10mm socket and wrench.

Have fun everyone. If you, like me didn't know about this component and its affect on A/C production, it might be worth a look.

Paul

 

OK I have to ask. What does a sensor in that position have anything to do with solar. sun never gets to that sensor.

 

It’s not a solar sensor, just call it a AC sensor. Obviously it measures the vehicle interior temperature and feeds back to the AC control assembly.

 

I am going to take one last stab at this and I know someone is going to call me an idiot. This is how I understand the AC Control system and I making a lot of statements and I am very willing to admit that I can be wrong.

The Lexus SC430 A/C control system uses all types of sensors and devices to allow the climate control system to give vehicle occupants the best comfort experience. One of those sensors is the cabin temperature sensor. Does it make sense that the control system needs to know the inside temperature of the cabin so it can adjust the AC system accordingly? That cabin temperature sensor is what BGW70 suggested cleaning. That is what DAVE01980 cleaned and now his AC is performing well. That is the sensor that RAVEN01750 cleaned. This sensor is in an air stream and measures cabin air temperature. It makes sense it would get dirty because air is flowing across the device. If it is dirty and can't accurately determine the cabin air temperature, the AC system will not operate properly. Am I crazy or not?

Now, just considering the solar sensor, which is a separate device, I'm going to include a page from a Toyota AC manual that discusses the solar sensor.



The document states that "60 % of the heat entering the vehicle comes from solar radiation". Wouldn't it make sense for the AC system to how much solar radiation is entering the vehicle so it could adjust the AC system accordingly?

It further states that the solar sensor is usually located on the top of the instrument panel. Take a look at the picture of the solar sensor. Doesn't it look like that device on the top, right of your instrument panel?

Further in the reading, it states, "Like a temperature sensor, the solar sensor (deleted tech stuff) senses the solar heat entering the vehicle. The AC ECU can adjust the outlet air temperature based on changes in sunlight before the interior temperature changes." If you have sat in a vehicle and the sun is beating down on you, you feel hot, even if the inside air temperature is satisfactory.

RAVEN01750, that page in the description of the solar sensor, mentions the passenger circuit. If you keep flipping through that manual section, it shows that there is a solar sensor output for the driver side too. That makes sense, have you sat in a vehicle where the sun is on you in the driver's seat and the passenger seat is in the shade?

Reading further, "Some Toyota vehicles use a solar sensor that measures sunlight fall from two angles to provide additional control over both the driver and passenger seating areas." In one of my original posts, I asked the question, does the Lexus SC430 uses a single sensor for this input? I think that might be the case, but I don't know and no one answered that question.

So, the system uses a cabin air temperature sensor and it is located on the driver's side, underneath that kick panel, adjacent to the driver's right knee. the sensor can get dirty.

The system uses a solar sensor to measure sunlight because the system needs to know the solar load to keep occupants comfortable. Just as GMANSC and IOLMaster mentioned, that sensor needs to be in a location to sense solar radiation. Wouldn't the top part of the dash be a good place for the device? That wiring diagram I posted above would indicate that the device is located on the top right side of the dash. Am I wrong?

DAVE01980 started the tread by asking about the solar sensor and I tried to answer just that question. BGW70, because of his knowledge and experience said, "take a look at that cabin temperature sensor, that may be the problem". Turned out he was right.

I think one of the confusing points was that this solar sensor does two things, it measures light and thus can offer sensory input for the headlight system, but it also provides sensory input for the AC system. That is why in the wiring diagram location the device is listed as "Light Control Sensor and AC solar sensor". That sensor may turn on or off the automatic headlights because it senses light. Your AC is still going to work in the light or dark, but if it is a sunny day, it might work a little harder because it senses additional solar radiation.

Just to further beat this dead horse, another device that has a dual purpose is the ambient (outside) air temperature sensor. That device is located in front of the radiator. It is connected to the Engine Control Module. One of the needed engine parameters is ambient temperature. It may change the air-fuel ratio due to outside temperature. The engine needs to know the ambient air temperature to provide proper performance. However, the AC system also needs to know the ambient air temperature so it can adjust the AC and heat controls. The Engine Control Module can communicate with the AC ECU by means of the Multiplex communication system. Different modules can communicate with one another through this communication network to provide sensory inputs from one another (or at least I think that is the way it works).

 

Got it Cinc04. One sensor (on dash) is the one and only Solar sensor. Through the magic of computers and the interconnecting CAN Buss, it talks to different modules acting like multiple virtual sensors. About right? Anyone ever see a logic table for our various computers?

Paul

 

Does anyone know how to replace the automatic light sensor on top of the passenger side dashboard?