Where is my solar sensor located and how do I replace it?

 

Good Morning Dave! First. Lets back up. Your profile says you have a GS350. Are we talking that vehicle or an SC430? What year? 08? Next, the sensor (Automatic Light Control Sensor A26) is the red round looking thinking sitting on top of the dash, passenger side, close to the windshield. "IF" that sensor has failed, you should have a trouble code (DTC) of B1244. Do you have a B1244 DTC code? I'm asking for a reason. That sensor isn't known to fail. It could of course. Unfortunately, that sensor is fed from/to the "Drivers Side J/B ECU. "IF" it is the ECU, it will be the second one I have called out in two days. Which is unusual because I have never had anyone present a problem that led me to believe that the ECU would be bad. You can easily test the sensor by turning on your lights to the automatic position during the day. The lights should be off. Cover the sensor with something that blocks the light. The headlights should come on. If not, THEN you can go from there. The sensor uses a data signal to communicate with the Drivers Side J/B ECU digitally. So unfortunately, a multimeter won't suffice for testing. Get back to us and we will sort this out.

Paul

 

Interesting—my SC430 automatic headlights stop working; but it did not trigger a B1244 DTC code…

 

That is interesting. I would then back up to the "combination switch" C11. I "assume" that the switch is all the way FWD in the automatic position. This sends a signal back to the Drivers Side J/B ECU. These are data signals though. This is pro stuff analysis that few shops have the ability or talent to do. No codes? I'm still digging. Lexas docs are like learning the old style Military Tech Manual System. Section 5 is diagnostics. The Electrical is acceptable. But takes time to go back and forth. I learn something new almost daily from the service manuals. But, I am a bit of a freak about maintenance. So for me it's a requirement. And 40 years as an Electronic Tech for the U.S. Navy, keeps my analysis skills sharp. 😏

Paul

 

Wait. Are we talking about the "Headlight Beam Level Control"? Or are we talking about the lights coming on automatically when you go through a tunnel? LOL. That would be hilarious. 🤣 I'm talking about the latter just to be clear. 😁

Paul

 

Same advice I would give anyone to try first after fuses etc have been exhausted. When your ready, get on your hands and knees on the drivers side and give a try at a good whack right to the side of where you left foot normally sits. It is intermittent after all. Worth a shot. 😏

Paul

 

Sorry profile needs updating and I drive a 2003 SC430. Ok I will try that test and to see if the lights come on. My dash is black and wondering if the sun is heating it up too much and that is why the AC goes warm and then cold once the car is cool.

 

Isnt there another sensor on the drivers side left in the floor or under the dash?

 

Im talking about the AC not turning on cold. I read somewhere the solar sensor has something to do with this. Sorry if I didn't explain that.

 

there is a sensor on the drivers side, right knee, in the dash. It’s for the HVAC temp.
you could pull it and clean it…it will be dirty

 

Boy did I go down a rabbit hole... 🤣

Paul

 

Do I need a tool to pull it out? I can use my hands?

 

Deleted. Thanks.

Paul

 

take a look at the pics in this thread…I think you remove the panel…been a few years ;-)
https://www.clublexus.com/forums/sc4...l#post11046191

 

I have been following this thread and I am really confused. So, why don't I weigh in and confuse things further?

Your original question asked about the solar sensor. The solar sensor measures solar radiation. The air in the car does not heat up immediately in bright sunlight so the solar sensor measures sunlight and helps the AC system anticipate the need for increased cooling. The sensor is not a thermistor, but a photodiode. It is located on the top right side of the dash. I don't believe your "dash heating up" would cause the problem.

As mentioned above, those sensors are very reliable. Have you tried to get diagnostic trouble codes? As mentioned above, if you pull DTCs you will get a code of B1421 for the passenger solar sensor problem and B1424 for the driver's side solar sensor problem, according to my manual. If you get one of the codes, the next step is to test the sensor(s). My repair manual gives the procedure for testing the solar sensors, but it is too detailed to give the complete procedure here. You basically remove the AC amplifier assy, turn the ignition on, measure voltage between the solar sensor terminals, and determine if voltage values are within spec, with the sensors exposed to a strong light and when the sensors are covered with a cloth.

In the thread, temperature sensors were discussed. The AC temperature sensors include the cabin air temperature sensor, the evaporator thermistor, and the ambient air temperature sensor. DTC for the cabin temperature circuit problem is B1411. For the evaporator temperature circuit problem, the DTC is B1413. For the ambient air temp circuit problem, the DTC is B1412. Have you gotten any of those codes?

Bgw70 mentions the sensor, "drivers side, right knee, in the dash. That is the cabin air temperature sensor. If it is dirty, I believe it could cause the AC to malfunction.

Getting back to your question about the solar sensor, I was looking at my repair manual and the SC430 is equipped with a solar sensor for the driver side and the passenger side. I cannot find where it shows two separate sensors, but I did read that some Toyota/Lexus vehicles use a single sensor that measures sunlight falling from two angles to provide control for the driver's and passenger's seating areas. I'm wondering if that is the case for the SC430. If that is the case, that sensor is on the top, passenger side and provides for both the driver and passenger inputs. I'm sure someone in the forum can confirm or correct me.

You asked about the removal of that sensor. My manual doesn't give specific instructions. I did see a reference on the internet that showed you can take a thin screwdriver and pry the sensor up and away from the dash. The screwdriver should be taped to protect the dash. It looked like you can disconnect the electrical connection once you have it lifted up from the dash. Now, I am going to add all kinds of warnings. I have not done this. I would be very, very careful in attempting this. I'm sure someone in the forum has done this and can confirm or correct me.

The SC430 uses an AC ECU which uses input from several temperature sensors, exhaust gas sensor, solar sensors, refrigerant pressure sensor, engine speed, compressor lock circuit, etc., and then controls compressor operation, five separate damper devices, blower speed, etc. In short, it is difficult for the average Joe to diagnose AC problems. A lot of times it's not the device that is causing the issue, but the connections. A bad wiring connector, a loose wire, a bad ground, etc.