Mirror compass display brightness varies randomly

[WarGawd]

Title pretty much self explanatory. In the 10 months I've had the truck, I've noticed maybe a couple dozen occurrences while driving at night where the compass display will briefly increase in brightness. Usually only lasts long enough to catch my attention, and just as I glance over, it dims back to normal again.

There may have been one or two times where I picked up on it during the day, but memory is kind of vague on that. I have noticed a brighter display intensity during startup, but then this usually stays constant afterward.

Not a huge deal, just a little annoying to not know why it does this...anyone?

 

[dmanns67]

I have noticed the same thing with my display as well. I just assumed that the light for the display was tied to the electric photocell on the dash board that detects lights. The display will adjust based on the amount of light it picks up. I cannot explain why that would happen at night. Not sure if the photocell could pick up light from other vehicle's headlights.

 

[WarGawd]

I have noticed the same thing with my display as well. I just assumed that the light for the display was tied to the electric photocell on the dash board that detects lights. The display will adjust based on the amount of light it picks up. I cannot explain why that would happen at night. Not sure if the photocell could pick up light from other vehicle's headlights.

Thanx - I was thinking along those lines as well, but sort of ruled it out because there usually seemed to be no other varying light source around to be reacted to, and I have specifically watched for it to change when encountering oncoming vehicle headlights. Also doesn't seem to be tied to any change in indicated compass direction??

Stuff like this makes a guy feel kinda naive doesn't it

 

[dmanns67]

Thanx - I was thinking along those lines as well, but sort of ruled it out because there usually seemed to be no other varying light source around to be reacted to, and I have specifically watched for it to change when encountering oncoming vehicle headlights. Also doesn't seem to be tied to any change in indicated compass direction??

Stuff like this makes a guy feel kinda naive doesn't it

Now that I think about it, I have the automatic dimming rear view mirror and I believe there are sensors in the front and behind the glass of the mirror. I wonder if the brightness of the compass display is tied into the automatic dimming feature? I would think items hanging from the rear view mirror might affect the sensor as well, i.e. parking pass. This could be tested by turning off the auto dimming function by holding the on/off button until the green indicator light turns off.

 

[Mark20]

I've had this since I got the Voy in 2005. At first I disconnected and reconnected the mirror's electrical connection but that made no change. Someone once mentioned to me that Mercedes (?) puts a red LED on the rearview mirror to help keep you awake at night. Maybe - just maybe - GM did something similar and randomly brightens the readout to help keep you conscious behind the wheel. That, or they've got a bug in the software.

 

[WarGawd]

Now that I think about it, I have the automatic dimming rear view mirror and I believe there are sensors in the front and behind the glass of the mirror. I wonder if the brightness of the compass display is tied into the automatic dimming feature? I would think items hanging from the rear view mirror might affect the sensor as well, i.e. parking pass. This could be tested by turning off the auto dimming function by holding the on/off button until the green indicator light turns off.

Any chance you know the RPO code for the auto dim mirror? I didn't think my vehicle had that, but there does seem to be a sensor on the backside of it...maybe mine is malfunctioning. I tried tonite to shine a flashlight directly at it and watch for a response, nothing seemed to change

 

[dmanns67]

Any chance you know the RPO code for the auto dim mirror? I didn't think my vehicle had that, but there does seem to be a sensor on the backside of it...maybe mine is malfunctioning. I tried tonite to shine a flashlight directly at it and watch for a response, nothing seemed to change

DD7 : MIRROR I/S, R/V, LT SENSITIVE, COMPASS. I was going to try that myself and see if the brightness changed.

DD8 : MIRROR I/S, R/V, LT SENSITIVE

 

[Denali n DOO]

Any chance you know the RPO code for the auto dim mirror? I didn't think my vehicle had that, but there does seem to be a sensor on the backside of it...maybe mine is malfunctioning. I tried tonite to shine a flashlight directly at it and watch for a response, nothing seemed to change

I looked at mine last night, when the mirror dimmed the display stayed the same. I don't know if the dimmer switch dims that display as well like it does to the radio, after thought I should have checked that too.

 

[WarGawd]

I checked my RPO code - DD4 - ISRV MIRROR W/COMPASS - so it is a non dimming mirror. Maybe what I thought was a sensor is just a location in the (common) mirror housing where a sensor would be placed.

And the behavior is that the compass display brightens briefly before returning to its normal intensity, which doesn't seem to be consistent with any kind of dimming function.