Modifying or disabling auto-dim mirror feature?

[Jim-K]

'04 GMC Sierra 2500HD. I have the auto-dimming rear and driver side mirrors. In some cases they dim too much. I recently drove thru Atlanta on I-75 after dark and the mirrors got so dim all I could see were spots of light in a dark blue background. I couldn't even make out shapes so I didn't know whether those spots were cars, trucks, or two motorcycles. It made it very difficult and, therefore, unsafe to change lanes. Is there any way to limit how much it dims the mirrors? I'd still like to be able to see the general outlines of the vehicles, lane markers, etc.

[GM-Tech]

There's no adjustment but it can be turned off. Look in your owner's manual as I don't recall the exact button to press on the mirror to do this.

[pwall]

I wish there was a way to turn it on....I find that sometimes the mirrors don't dim when I wish they would.

[GM-Tech]

I wish there was a way to turn it on....I find that sometimes the mirrors don't dim when I wish they would. 

 

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Put a piece of electrical tape over the light sensor.

[Jim-K]

There's no adjustment but it can be turned off.  Look in your owner's manual as I don't recall the exact button to press on the mirror to do this.

 

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I checked the owner's manual - couldn't find a thing except a brief paragraph that said the mirrors automatically dimmed. That's why I posted here.

[GM-Tech]

I checked the owner's manual - couldn't find a thing except a brief paragraph that said the mirrors automatically dimmed.  That's why I posted here.

 

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The following is from an '04 Sierra owner's manual. It covers turning off the auto-dimming as I mentioned...

 

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Automatic Dimming Mirror Operation

 

The automatic dimming mirror function is turned on automatically each time the ignition is started. To operate the automatic dimming mirror, do the following:

 

Make sure the green indicator light, located to the left of the on/off button, is lit. If it's not, press and hold the on/off button for approximately six seconds until the green light comes on, indicating that the mirror is in automatic dimming mode.

 

Turn off the automatic dimming mirror function by pressing and holding the on/off button for approximately six seconds, until the green indicator light turns off.