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3rd brake light acting funny

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Old 02-23-2013, 11:41 AM
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3rd brake light acting funny

So I took my third break light lens off and switched it with a blacked out lens cover. Now it doesn't work like it should, or like I believe it should. The lights does not light up on breaking or when truck is in reverse. It only comes on and lights up when I open my door or unlock my doors. Anybody know why this is or how to fix it? Also my heated mirrors don't work. They don't melt the ice off of the mirrors and I checked the fuse and it's just fine.
 
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Old 02-23-2013, 12:47 PM
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Never had one light up in reverse....just when opening the doors. The red center portion should work with the brakes applied. Might check for power at the bulb.

As for the mirrors, I would see if power is being delivered to the plug when it should be also.
 
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Old 02-23-2013, 01:10 PM
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How would I do that? Can I just out another bulb in there and see if it lights up? And how would I check the power to my mirrors? I know this all sounds newbie style but I'm not an electrics guy. I'm all engine.
 
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Old 02-23-2013, 09:38 PM
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Get a digital volt meter good for 12 volts dc. Locate a wiring s thematic and track down the power wire colors for each item. Then check for power at those wires at the plugs.

If you try a new bulb and it works...that is fine for the light. If it does not work you still will not know what the issue is. Also...You need a meter to check the mirrors.
 
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Old 02-24-2013, 07:58 AM
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If all you did was swap a lens, you probably disrupted the ground for the bulb circuit. Your symptoms are of an open ground. Pull it out and check to see if any wiring was damaged.

The mirror heater circuit uses the same ground connection back in the LH C-pillar.
 
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