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Discussion Starter · #1 ·
I do not like the way that my ambient light sensor works. In the morning it will not turn off the headlight until about 2 hours AFTER sunrise, And in the evening it will turn the headlights on about 2 hours before sunset. To me this seems excessive. I do not need headlight while I am still needing sunglasses. The interesting part of this is that if it is cloudy, the lights work more as one would expect.
When the headlights are still on during that period the sensor is getting direct sun shine on it.

Sooooooooo............
I am assuming that the light sensing element in there is a photo resistor of some kind. A photo resistor changes its resistance depending on just how much light is hitting it. It will have a high resistance when it is dark and a low resistance when there is light. So my plan is to splice in a variable resistor in parallel with the photo resistor to lower the resistance that the computer sees so that I can adjust the headlights to go on and off at a more appropriate (to me) light level. Since the sensor is cheap I plan to go to the bone yard to get an extra sensor and a few inches of the wire harness and the connector so that I can make my mods there and not have to cut into the factory wires.

My first questions are;
1. Does any one have the specs on just what kind of element is actually in there?
2. Does anyone know what the threshold voltage (or resistance) is where the lights change state?
3. Is there a place where I can get at the wires without pulling the dash apart?
 

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I don't know if the sensor is a photo-resistive type, or a photo cell, or less likely, a photo diode. We're all waiting for you to let us know.

I don't think the whole dash has to come apart. You can probably get to the wiring by pulling the radio.

I've noticed the same guessing that the sensor goes through. I have used light meters that would require letting the sensor rest for a while if it was pointed towards the sun. I don't know if it was the circuit the sensor was in or the sensor itself that got saturated from too much light. The circuit was usually designed to increase the sensitivity for light measurments, so it adversely affected the accuracy when saturated.

If you're going to do this it might be simpler to use a variable resistor or maybe just a switch for high and low sensitivity for dawn and dusk. For the existing circuit the sensor feeds there should be a capacitor that charges up via the voltage from the sensor. Whenever it gets near a threshold voltage the lights turn off. Otherwise the lights are on. I'm sure that it's designed to turn lights on if there is any question whether or not lights are needed.

Ted
 

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Ted, I am familiar with your smart meter; Flyin, your meter seems to be a bit above average (hmmmm, maybe that's the problem).
Guys, your over thinking it, these things work, why not just get a new one and call it a repair well done.

The two vehicles where I replaced the sensor, both had a piece of dash, next to glass, that lifted and allowed easy access.
The sensor will also pull up, out of the dash.
 

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I have a feeling if I replace it it will work exactly as it does now. I think it's working as designed; weighted towards lights being on for safety. The real problem is the gauges and radio switch to night mode which makes them hard to read with sunglasses on.

My Mom and Dad both were plagued with cataracts when younger than I am now. They never liked wearing "shades", especially when fishing. I think I've kept my eyes in great condition by always having my Polaroid sunglasses close at hand. I have a pair that stays above my visor. I can't remember the last time I've had to use the visor. I'm not sure I've ever used it in the truck.

Ted
 
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Hmmm, I get a lot less sun that you (steeper angle), today is cloudy, will be raining in a few hours and about 2 hrs away from sundown.
I just drove across town and had no night time problems.

So, sitting in my truck while I type. Started the truck and the lights were in the day mode. Waited a min, or two and the lights stayed in day mode; so, I tossed a newspaper over the sensor, about 10 secs and we switched to night mode.
Waited a couple of mins and removed the paper, took 10 sec to switch back to day mode.
Mine seems to work as I would expect.
 

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Discussion Starter · #6 ·
As I mentioned, on cloudy days it does work as one would expect, It is on the clear blue sunny sky days that it does not work correctly. This does make sense. with a clear blue sky and the sun very low in the sky the suns rays are hitting the sensor at a very steep angle so it is not actually seeing that much light. with some clouds in the sky it diffuses the light so that sunlight that is reflected off the clouds is hitting the sensor at a much better angle, so the sensor does actually see more light on a cloudy day.

I think I am going to see if I can get a sensor and a connector with pigtail from the bone yard to experiment on. Just so that I do not have to go into the dash any sooner than necessary. Many say that I can just pop out the radio and reach the sensor and many others are telling me that I will have to pull the dash to get to it.
 

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