Dimmed Backlit Dash and Radio/HVAC Lights

[EddieC]

My 2008 Tahoe backlite dash/instrument/radio/radio lights seem to randomly get very dim and a while later they brighten up to normal without any input on my part. This occurs (randomly??) during the daylight and I don't know what could be causing it or how to fix it.
Any ideas?

 

[Miami-Dade]

@EddieC Moved you here from 15-20 section.

 

[Shubbydog]

Sounds like a failing dimmer switch.

 

[Doubeleive]

could be the switch, should be cheap and easy to replace

 

[EddieC]

@EddieC Moved you here from 15-20 section.

Thanks, I missed that.

 

[mikez71]

Shouldn't it be the light sensor/circuit since the dimmer only works at night?

Dim backlight has been bugging me more since I got a dashmat.
The sensor has a resistance of ~600ohms in direct sunlight, and 15,000ohms in full dark. Not sure the exact setpoint, but 10k ohm will put it in dimmer mode IIRC..

I'm planning at least one of 3 things (maybe combo of all...)

1. switch with day/night resistors to manually select brightness (or mode)
2. relay with day/night resistors triggered by the parking/headlights
3. resistor wired in parallel from light sensor input to ground, to de-sensitize light sensor.

 

[Doubeleive]

Shouldn't it be the light sensor/circuit since the dimmer only works at night?
Does the dimmer dial work when it's dim?

Dim backlight has been bugging me more since I got a dashmat.
The sensor has a resistance of ~600ohms in direct sunlight, and 15,000ohms in full dark. Not sure the exact setpoint, but 10k will put it in dimmer mode IIRC..

I'm planning at least one of 3 things (maybe combo of all...)

1. switch with day/night resistors to manually select brightness (or mode)
2. relay with day/night resistors triggered by the parking/headlights
3. resistor wired in parallel from light sensor input to ground, to de-sensitize light sensor.

the interior/cluster/door switch/panel lights are on day or night, they just dim at dusk
in any case the switch controls the brightness and headlight switch turns them off to this
the lowest you can get the interior is to this, the ppv's might have a option to turn that off also

 

[mikez71]

Right, sounds like his go nighttime dim in the day.?
My dimmer only works in nighttime mode..??

FWIW, AutoSync w/BCM option can reprogram dimmer brightness. So full dim can be fully off.

 

[Doubeleive]

Right, sounds like his go nighttime dim in the day.?
My dimmer only works in nighttime mode..??

FWIW, AutoSync w/BCM option can reprogram dimmer brightness. So full dim can be fully off.

the dimmer should work anytime, just harder to tell in daylight (try covering the cluster with a piece of cardboard to shade it then adjust the knob to see)
but... I could be wrong this has come up before in the past, I think the issue was not being able to turn off the lights during the daytime because they are always on

 

[Scrappycrow]

The dimmer works in daylight, and it's easiest to tell if you watch the radio screen while turning the knob.

 

[EddieC]

Right, the dimmer knob (or shaft) works day or night. At the end of the rotation the dome lights turn on.
My problem is that the dash lights randomly dim themselves without my touching the dimmer,
When I say randomly, it's just that. It could go many days and then dim and come back to the setting 5 or 10 minutes later. It's not like it's constantly flashing dim and bright.

 

[mikez71]

Just checked mine. No dim at all in the daytime.. What would the issue be?

 

[PPV_2018]

Do you have anything on your dashboard? I’ve found with other vehicles that an obstructed auto-headlights sensor by means of a dashboard cover or even dark tinted windshield can cause dashboard lights to do some weird things including dimming all the cluster and control lights in the daytime intermittently.

 

[Doubeleive]

dimming is usually affected by the sensor on the forward part of the rear view mirror on drivers side
put your finger over it and the lights will dim
most likely would not be the cause for flickering or any other weird stuff though, unless you had a air freshener or a sticker or something obstructing it

 

[mikez71]

i have a dashmat now, so the dimmer is more active, but daylight mode the dimmer does not dim. Only in night mode...???

 

[Doubeleive]

i have a dashmat now, so the dimmer is more active, but daylight mode the dimmer does not dim. Only in night mode...???

it doesn't do much at all in the daytime maybe you just are not seeing it, try using a piece of cardboard to cover the radio or cluster and adjust the dimmer

 

[mikez71]

I will check again tomorrow, -BUT- if it's that hard to notice, then I don't think that's what the OP is experiencing.
If he is seeing much dimmer backlight in the daytime, which would not be achievable with daytime dimmer.

From what I can tell looking at wiring diags, the sensor in the mirror maybe for dimming mirrors, and the solar/ambient light sensor in the dash controls daytime/nighttime.

Either way, I know the ambient light sensor controls the dimmer in my 2012...

 

[Doubeleive]

I will check again tomorrow, -BUT- if it's that hard to notice, then I don't think that's what the OP is experiencing.
If he is seeing much dimmer backlight in the daytime, which would not be achievable with daytime dimmer.

From what I can tell looking at wiring diags, the sensor in the mirror maybe for dimming mirrors, and the solar/ambient light sensor in the dash controls daytime/nighttime.

Either way, I know the ambient light sensor controls the dimmer in my 2012...

you are thinking of the rear mirror sensor, it has 2 sensors one you can see when look in it and one on the (backside) "front" facing the front window.
the one you see when looking in the mirror is to detect headlights behind you and dim the mirror and drivers side mirror.
the sensor in the dash is the "sun" sensor it controls the hvac and headlight activation, when the headlights activate dimming also activates

 

[mikez71]

*Maybe* why my dimmer doesn't work in daytime..
My auto headlights are disabled.. (Autosync BCM programming)


Or not, looks like this guy had the same dimmer behavior..

Dash light dimming during the daytime?

09 LTZ - is there a way to turn off or dim the damn dashlights during the daytime? The dimmer only works when the sensor on the dash turns on the lights? Thanks

www.tahoeyukonforum.com

And I don't remember them ever dimming in the daytime...Weird

 

[Jetskier77]

Mine did the same exact thing... randomly going brighter, dimmer, etc. It would often be fine for weeks or months at a time, then go wonky. Replaced the combo headlight/dimmer switch and problem resolved.