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Discussion Starter #1 (Edited)
So I've been frustrated lately with the Ambient Light Sensor's understanding of how it thinks things should look vs how they actually look, lol.

I believe its function and my frequent North <-> South commute are not getting along well as a few minutes of shadows triggers the dimming of the DIC, MyLink and interior controls and then the remaining light that peaks through the trees, buildings, A-pillar, etc. on the way to work and back is often not steady enough to trigger the system that there is enough light to switch back to full bright. I'm often finding that the A-Pillar is shadowing my sensor and causing me to go or stay dim when it's perfectly bright out.

Some have found that their sensors were bad but I'm pretty confident that mine is working just fine as testing showed that the sensor would switch back and forth in just about 20 seconds when covered or uncovered in direct light.

Here's where I note that I take no responsibility for you screwing up your truck. If you choose to follow this guide you do so at your own responsibility.

I looked in the Electrical Upfitter manual and the Ambient Light Sensor (B10B) is shown to have 2 circuits that seem to control the brightness and how frequently it should be switching back and forth:
PIN 4 a yellow/violet wire the "Twilight Sentinel Delay Signal"
PIN 5 a white/blue wire the "Ambient Light Sensor Signal"

I thought that adding a switch to PIN 4 the, Twilight Sentinel Delay Signal, would hopefully remove any trigger that would dim the interior brightness...unfortunately this seems to have no effect on the brightness level but somehow must act as a averaging when you cross frequently between bright and shaded areas to know if there is more bright or shade and whether it should switch or not. - Not enjoying its current programming logic, obviously, lol

So I tried PIN 5 the Ambient Light Sensor Signal wire itself. Good news is that if there is no signal on this circuit the dash stays at full bright always. So I wired a switch into this circuit and viola I can now override the dim on demand. With the switch (circuit) closed it operates normally, dims when dark or shaded and if you want to override the dim just open the switch and in about 1-2 seconds youre back to full bright.

I tested with the headlights on and off and there is no change nor are there any errors or alerts from manually opening the circuit.


Here's where you learn from me ripping my entire dash apart today. You don't need to fumble around trying to monkey the sensor out of the dash like I did. The sensor wires are available right behind the radio face plate so you can splice in there as long as you have enough room to work.

This is a pic of the sensor itself and it harness. You can see the PIN 5 white/blue wire I removed from the harness in testing.



This pic unfortunately turned out worse than I was expecting :frown2: but this is the section of the Ambient Light Sensor wiring harness that is right behind the radio faceplate. You cant tell from the crappy pic but it's the small left most section in that splits off the bunch and routes back into the dash toward the front of the truck to the sensor.



Since I had the dash apart I pulled the entire harness out as it was easier to work. Here is the wiring with the sheathing pealed back for access. You can see the while/blue wire. I cut this and wired in a PIAA light switch I had laying around. I plan to add a better switch once I decide on where I want to permanently place it.



And that's pretty much it. Button up your dash and you can now override your brightness when the auto dimming isn't "mathing" right, lol

Here's a video in operation (you will need to click it to watch).

***EDIT*** Video was made inaccessible by PhotoBucket so it has been deleted.



The video starts out on full bright with the sensor in the light and the circuit closed (everything working OEM) you can see the MyLink is full bright, DIC behavior is the same as the MyLink, I just couldn't get it in the shot.

At about 5 seconds into the video I cover the sensor, it takes about 20 seconds to switch to dim to night brightness (ignore the flickering it's just the camera nothing in the truck is flickering). Once on dim I open the switch and in about 1-2 seconds I go back to full bright with the sensor still covered. Click the switch again and 1-2 seconds back to dim and then one last open.


Hope y'all enjoy this as much as I'm gonna :grin2:
 

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Wow, thanks for this. I don't feel comfortable doing this myself, but I'm hopeful that perhaps this is the first step in getting some action from GM. Maybe we can get them to admit that there is a problem with this and actually agree to fix it. That's my hope anyway.

Excellent work. You are doing God's work, son.
 

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Discussion Starter #3 (Edited)
Wow, thanks for this. I don't feel comfortable doing this myself, but I'm hopeful that perhaps this is the first step in getting some action from GM. Maybe we can get them to admit that there is a problem with this and actually agree to fix it. That's my hope anyway.

Excellent work. You are doing God's work, son.
Thank you sir.

Yeah I wasn't going to hold out for a "fix" from GM. IMO Unfortunately there are just conditions in the real world that I don't think GM can really program for without adding more sensors to re-evaluate lighting conditions from more that one location. :frown2:
 

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Is disabling the sensor essentially the same as manually cranking the brightness knob up, but easier and without having to fiddle around to dial the dim setting back to the correct level when it's time for dimming? Is the brightness the same with the sensor disabled as it is when the dial is turned up?

I've only seen this happen a couple of times, so I haven't really poked into the problem much.
 

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Discussion Starter #6 (Edited)
After the mod does the brightness adjustment wheel operate in both modes?
I did not bother trying to work the brightness wheel because IMO the purpose of it is to set it where you want the night brightness level to be and leave it. Not to have to be fumbling around with that wheel all the time to compensate for crappy sensor logic.

Either way when you have the circuit closed this is normal OEM operation so everything should work normally. IMO you would only open the switch to get full brightness during those times the sensor was not giving you the full brightness you need so IMO it's not like you'd want to leave this active (switch open) all the time. But, I will check to see if that rheostat has any affect when the switch is open anyway later today when I go out.



Is disabling the sensor essentially the same as manually cranking the brightness knob up, but easier and without having to fiddle around to dial the dim setting back to the correct level when it's time for dimming? Is the brightness the same with the sensor disabled as it is when the dial is turned up?

I've only seen this happen a couple of times, so I haven't really poked into the problem much.
Should be yes, see above :grin2:
 

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I just got back from buying more truck stuff, and I noticed the sensor doing it's thing. I turned the adjustment dial all the way up, but the display didn't seem bright enough. When I got to a sunny area, the sensor stopped dimming mode and the display got much brighter. So your switch mod does more than just turning up the dial can do. I'll have to add this to my list of Must Do! projects that I never do. :)
 

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Discussion Starter #9 (Edited)
Can that harness be accessed anywhere without having to remove the dash?
Not that I'm aware of

@GeneT

I just tested the rheostat with the OEM circuit enabled and disabled and in both conditions in true full bright the rheostat (dimmer wheel) does nothing. It only adjusts the brightness level when in "night" or "dim" mode. So sorry to be the bearer of bad news but if youre thinking youre in full bright mode but able to affect the brightness with the wheel, then maybe you have a bad sensor because youre not really in full bright. :serious:

I just got back from buying more truck stuff, and I noticed the sensor doing it's thing. I turned the adjustment dial all the way up, but the display didn't seem bright enough. When I got to a sunny area, the sensor stopped dimming mode and the display got much brighter. So your switch mod does more than just turning up the dial can do. I'll have to add this to my list of Must Do! projects that I never do. :)
Definitely, true full bright is still way brighter than the rheostat adjusted to max in "night" or "dim" mode
 

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Not that I'm aware of

@GeneT

I just tested the rheostat in with the OEM circuit enabled and disabled and in both conditions in true full bright the rheostat (dimmer wheel) does nothing. It only adjusts the brightness level when in "night" or "dim" mode. So sorry to be the bearer of bad news but if youre thinking youre in full bright mode but able to affect the brightness with the wheel, then maybe you have a bad sensor because youre not really in full bright. :serious:



Definitely, true full bright is still way brighter than the rheostat adjusted to max in "night" or "dim" mode
Thanks for the info. I may try this mod if I ever feel confident enough to remove the dash!
 

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Discussion Starter #11 (Edited)
Ok so who wants to read the weirdness? lol

Since Ive had this "option" (2 days so far) I haven't even had to use it. :serious: lol

I have a couple suspicions as to why.

1. The sun is setting earlier and the shadows are now at just different enough angles to not be acting on the sensor exactly the same way

2. Splicing in the extra wiring and switch added just a tad more resistance to the circuit that makes it actually work better, lol


Guess I'll be playing it by ear for a bit, haha
 

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I WILL be gearing up to do the same mod soon. Can you tell me exactly what kind of switch including brand and model you will be using? Thanks
 

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Discussion Starter #14
I WILL be gearing up to do the same mod soon. Can you tell me exactly what kind of switch including brand and model you will be using? Thanks
It's irrelevant (as long as it's not labeled "momentary") pick anything you like the looks of.
But if it really matters to you I just picked some of these cheapies and will likely mount it in the plastic panel under the light switch

 

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Would it be possible to fabricate something like a little felt lined cup over the sensor with a LED that would be bright enough to over-ride the dimming parameters without having to do any real wiring mods or open up the dash.
 

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Discussion Starter #16
Would it be possible to fabricate something like a little felt lined cup over the sensor with a LED that would be bright enough to over-ride the dimming parameters without having to do any real wiring mods or open up the dash.
Post number 73.

Besides you try reaching up there while driving
 

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Does anyone know if the light detector on the sensor pointing into the cabin or out thru the windshield? I see a red lense on the cabin side.
 

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Discussion Starter #18
Does anyone know if the light detector on the sensor pointing into the cabin or out thru the windshield? I see a red lense on the cabin side.
Search and check out some of the other discussions on the topic.

Lemme know if you have any specific questions about this mod :wink2:
 
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