where to get 12v switchable power in '10 Sierra

slapshot · February 2, 2012

I'm going to a portable XM receiver in my Sierra. It has a lighter style power cord. I was to tap into 12v somewhere behind the dash and install a lighter plug back there out of sight. I tried to tap into a couple fuses today, and either I wasn't get a good power connection or ground connection. Where is the easiest place to tap into 12v on these trucks that turns on and off with the key??

8.1HD/ALLISON · February 2, 2012

On the floor, next to the parking brake, there is a juntion block with a cover on it. Should have a few wiring harnesses plugged in, and still have some open slots for other connectors. I believe on the left side near the bottom one of the terminals in there is switched. Be sure to install an inline fuse!

slapshot · February 2, 2012

I can use one of the "add a fuse" to get the power. Does anyone know which of the fuses is switched, or which fuse the radio is on? Finding a good ground under there is a pain too. I looked at some of the mounting bolts and they all have plastic around them.

Thanks 8.1, I will check that one out too!!

latreille89 · February 3, 2012

I tapped into the power wire for the 12v plugs. They are always on tho so I just have to turn off the Sirius when I'm not using it.

wottenad · February 3, 2012

I'm going to a portable XM receiver in my Sierra. It has a lighter style power cord. I was to tap into 12v somewhere behind the dash and install a lighter plug back there out of sight. I tried to tap into a couple fuses today, and either I wasn't get a good power connection or ground connection. Where is the easiest place to tap into 12v on these trucks that turns on and off with the key??

If you use the diagram below, keep in mind that the accessory pin (X14 pin 8) is rated at 2 amps ONLY - It WILL blow if you draw more than 2 amps!

If your accessory pulls more than that you MUST use a relay to switch a circuit with higher capacity.

If you can get your hands on a standard "Bosch" style relay, you can get up to a 25 amp draw from pin 5 by wiring it like this:

Terminal 85 - Ground (X14 pin 1)

Terminal 86 - Accessory (X14 pin 8)

Terminal 30 - Constant (X14 pin 5)

Terminal 87 - Out to your accessory's 12 v input wire