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Discussion Starter · #1 ·
Gathering the necessary equipment to add a light bar a la oneofakind's how to, and finding that most installations do not wire the power to switched 12v power. I'd like to wire mine to switched 12v, but I'm unclear as to what my options are in the engine compartment. Is the main power block switched, or a direct connection to the battery? Trying to avoid the switch leaching power while it's parked, and only have power available to the switch when key is turned to accessory. Any suggestions?
 

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Discussion Starter · #3 ·
The problem there is that the brights have to be on for the aux to illuminate - I want this switch to be independent of the brights.
 

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I'm not 100% sure that's a true statement but I'm happy to be wrong. I think SwissXC90 is correct.

30+ bus 11B/5 "should" be switched and turn off when the vehicle is turned off. Aux lights per EWD are relay controlled by CEM (grounding of C:9 I suspect since the other side of the relay is the same 11B) and the CEM communicates to the the interior switch via CAN. Whatever restrictions govern light activation when the aux lights are installed I'll guess come from the CEM, either directly or indirectly.

I'm pretty sure that the fuse 5 position is on if the key is turned (and vice versa) but give it a try and validate for yourself. At the front of the vehicle, the connector (54/8) pin 1 is the 12V side, and pin 2 of the connector is the return path to CEM (via the relay that would be plugged in and connect to the lights).

If this is indeed switched voltage as suggested when you check, wire pin 1 to the light bar hot side and find a ground somewhere on the vehicle, don't use pin 2 at all. Fuse 5 is supposed to be 20A per EWD.

Good luck and let us know if this works or not. Alternatively, you could try a piggyback on fuses 16 or 17 or 20 if that was more desirable but then you have to run a wire to the front.
 

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Yes aux lamps come on with high beams. But you could use the aux lamp connector, relay and fuse for you lamps, and then just cut the relay coil wire and control it however you want.


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Had a minute to check, my theory goes out the window since power to the aux light fuse is an "always on" 12VDC. Lights will be turned on by CEM grounding C:9 which in turn would pull down the relay (included with aux light kit).

Interesting to note that it's fuse 2 on the '05 and fuse 5 on the '08. Both are empty slots in my vehicles so a 20A fuse will need to be installed if this DC source is used (can put in less than 20A if you wish).

Could still connect the light bar to aux lighting connector 8/54 pin 1 for power, just need to run a return via separate conductor to a switch (10A+) that connects to vehicle ground for turning the light off and on.
 

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Discussion Starter · #7 ·
Looking at my engine compartment fuse panel, slot 4 is empty. I'm down a wing at the moment (shoulder surgery), but have reinforcements coming over thee weekend. Along with testing my battery for its health and CCAs, I'll be checking that slot for potential use. No use is indicated (even as an option), so hoping it'll be my winner.

The numbers (pins, connectors, etc) are throwing me for a bit of a loop, is there a diagram I'm missing?
 

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You'll have to find an electrical wiring diagram (EWD) for the designators, they're around on the internet I suspect. I've never seen a 2012 EWD, I'm going by a 2010 document. If fuse 4 gives you what you need, take it. Slot is for an auxiliary heater, suspect it won't be switched but see for yourself when time permits.
 
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