My headlights have been on when I thought they should be off because of plenty of daylight. I switched from auto to off and got a message on the DIC, "headlights recommended". It has happened on my wife's Lexus also.

 

I tried that with a flashlight a few times and nothing happened??

 

Same on my 08.???

 

Yep, the ambient light sensor pulls a double duty as the sun load sensor as well.

 

The lights will not turn off instantly when the sensor is shown bright day light. Hence it take a few mins for the lights to turn off instead.


So as stated, if the sensor sees the conditions as dusk lighting at all, and the lights are going to come on instantly. It's then when the sensor his exposed to the bright sun light long enough and sending the signal long enough, that the BCM will turn the lights off instead.


Really, the easy way to check the sensor, just turn the lights off via the light switch (and press the top right dash button to cancel the light suggested message in the DIC), and come dust/night, make sure that the car is turning the lights back on automatically isntead.

Hence sensor may be going lazy and it not sending back the correct voltage until the sensor has enough time to warm up instead.

 

The sun is out now CST 205 P/M.I'm going to put a black rag over the sensor and go for a ride, my lights should stay on if it's working.

 

Hey Bat, how are ya?

The exact same thing has happened to me, twice in around 5,000 miles. Been fine the last few months.

 

Would, could, should, are all tentative.

As state, if the sensor was bad, then the car should be throwing a B2647 code.

But the glitch is the sensor is being read through the HVAC controller by the BCM, hence the HVAC controller is the item that is supposed to be sending 5v in the first place to the sensor, then getting the differential reading back, then sending the sensor output voltage to the BCM via the GM land bus. I bring this up, since if the HVAC controller is sending less than 5v to the sensor to begin with, then the reading back from the sensor will be lower than it should be, and a false reading back to the BCM through the land bus as well. Hence as long as the voltage reading from the sensor is 2.4V at the lowest (even in bright light), the car thinks that the sensor is good.


Bluntly, Given half a chance with the center console out for any reason, it always a good idea to pull the Hvac controller to clean its board/connectors and check for any questionable solder joints on it at the same time (same goes for any connector that in the area that you are working in the dash as well).

And yes, the next time I have my HVAC controller out, will do a write up on it for what to look for/how to clean it up if it goes glitchly, so the only reason to replace it is when you wear the button decal off instead.


To add, had GM just used some dielectric grease on the electrical connections when assembling the car, it would have solved a lot of electrical gremlins cause by corroded connections as the car.connections gets older instead.

 

Another great post Dano.

I look forward to your tutorial about the HVAC controller.

 

Yep, got it the first three times .

 

 

May not be much difference in the noticeable light (your eyes adjust for lesser light so you may not notice a difference), but the sun angle is different. So at a low angle, it's going through more glass and more tint. I'll bet the tinted windshield is your problem. But if it just started happening, your sensor may also be weak.

I thought tinting a windshield was illegal anyway, except for the upper few inches.

 

I'm doing OK Bruce. I hope you are too.

Yeah, it has happened once in the Vette but since it happened in my wife's car also I concluded that even though I thought it was daylight enough it obviously wasn't.

On another subject, how's the weather in NY? The high here today was 91 deg.

 

Thanks Bat, doing ok.

Seasonal the past couple weeks, was down to 23* one morning.

But next week is "Indian Summer," will be sunny and in the 60s and 70s. Probably the last hurrah for us til next spring.

 

Dano thank you very much for the knowledge and suggestions. I guess bringing the car to reprogram would be the best idea since I can't figure out how to do the other suggestion with the voltage regulator. I guess I could live with it and just shut them off when they come up or I could remove my tint to see if that fixes the problem. In reality, it is not a problem. It just annoys me having to shu the lights off.

 

So much for thinking the tint was the problem... It's gone yet the lights are getting turned on as soon as the sun is setting.. I guess in the year I have owned the car, I never drove around that time to realize the lights come on auto as soon as the sun is setting..

 

This afternoon I was gassing up around 3:00. So after pulling out from under the canopy over the gas pumps I noticed my lights were on. They stayed on for at least 2 minutes then went off.

I was at the same gas station I always use, but this NEVER happens during the summer. It's just (apparently) because the sun is so much less intense this time of year.

I've noticed it on my road too, which is completely shaded. In the summer my lights always go off within a half minute of pulling out of the barn, but this time of year sometimes they stay on til I get out of this "hole" I live in, and get into direct, bright sun.

That's my theory and I'm sticking to it.

 

Is it possible the auto headlight sensor wasnt operating properly due to a dying battery?

I asked because my battery died this wknd. I got a new battery and this morning when I got into the car, the lights didn't not come on. Any other time under similar circumstances and time and temp, the lights would be on with the old battery. Relation?

 

Possible? Considering the reference voltage is converted down from the 12V battery down to 5V, if the starting voltage was lower then the reference would start lower also, but I would assume that once the Alternator turned on and took over then it would return to normal levels.

Unless the weak battery was bringing down the alt voltage also.

In other words, if it is working now with the new battery then all is cool.

 

Can anyone tell me if the headlight sensor could also produce a one time, brief flash in the headlights upon entering the garage and getting close to the back wall at night? I thought this could be due to the reflected light hitting the dash mounted sensor. Originally, I assumed it was a proximity warning but learned, upon research, that the C7 does not come equipped with this feature.