Constant 12V Power in Overhead Console

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ford141

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Here's my situation: I have a wireless phone charging mount that is suction-cupped under my rearview mirror. It's nice because I can snap my phone onto the mount and it charges and connects to my radio wirelessly and automatically. But I hate having the wire from the charger running down the face of the dash to the charging port that is plugged into the cigarette lighter. So, I took the USB charging port and moved it to the overhead console so I can run the charging cable up with the rearview mirror wires and everything is clean and hidden. I tapped into the constant 12V power for the map lights to power the USB port.

Unfortunately, as soon as I did this my Yukon's battery started dying overnight. It took me a few days to find out the source of the discharge since I was using the same USB port as I was before, just moved overhead instead of plugged into the cigarette lighter like it was before, but as soon as I cut the wires to the USB port my battery stopped dying.

Now, it is possible that the USB port just happened to go bad when I moved it, but it is a strange coincidence since it stayed plugged into the cigarette lighter for a year without any issues. But the map light power in the overhead console comes from the BCM module and therefore is monitored to protect the main battery voltage. If the USB port was drawing enough current to kill the battery, the BCM should have turned off the circuit, right. To test the function of the BCM, while the USB port was still wired into the map light circuit I left one of the map lights on when I parked the Yukon overnight, and the BCM dutifully turned off the map light circuit (and therefore the USB port too) after 10 minutes, and the Yukon's battery was just fine the next morning. Later that day I again parked the Yukon overnight, this time without the map lights on (therefore the USB port was still "powered" although was not in use) and again the Yukon's battery was dead the next morning.

Has anyone else tried wiring accessories to BCM-controlled 12v constant power? Or do I have to run dedicated 12v power up to the center console to power the USB port?
 

Doubeleive

Wes
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why do you need constant power? do you leave the phone in the vehicle overnight? if not then just hook it up to accessory power you can get a 12v to usb adapter and run the wire from the drivers kickpanel up behind the pillar and then under the headliner then when you turn the key off the charger goes off.
 
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ford141

ford141

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why do you need constant power? do you leave the phone in the vehicle overnight? if not then just hook it up to accessory power you can get a 12v to usb adapter and run the wire from the drivers kickpanel up behind the pillar and then under the headliner then when you turn the key off the charger goes off.

I don't need constant power, I was just trying to avoid having to run power wires up to the overhead console if I could pick up a good power source up there instead. That may be what I have to do though. Just baffled me as to why it kills the battery when I'm pulling power from a circuit that is supposed to protect the battery. I guess I may never understand why. Funny how those "simple" jobs end up taking WAY more time than they should to get it right.
 

Doubeleive

Wes
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I don't need constant power, I was just trying to avoid having to run power wires up to the overhead console if I could pick up a good power source up there instead. That may be what I have to do though. Just baffled me as to why it kills the battery when I'm pulling power from a circuit that is supposed to protect the battery. I guess I may never understand why. Funny how those "simple" jobs end up taking WAY more time than they should to get it right.
I have used a couple of these before makes for a easy clean install, just connect it at a suitable accessory power source.
https://www.ebay.com/itm/Micro-USB-...335979?hash=item214491f16b:g:DjIAAOSwjodaHlnO
 

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