Sometimes you need a 12V power feed for a piece of after market equipment. Getting one was quite an adventure. In the end, it didnt have to be so difficult, but hindsight is always 20-20.
First I asked Washington D.C. service. They were very non-comittal, citing advice from their lawyers (weak excuse). I wanted a switched 12v source, that would turn off when the car turns off. Turns out, the 12v cigarette lighter plug in the Model S does switch off when the car powers down. That's good. So I figured I would get 12V from the back of the cigarette lighter plug, as I needed it near the center console anyway.
NOT SO FAST! I set about taking apart the trim on the center console. The carpet on the bottom is simply pried out, attached by a novel kind of velcro. There are 2 bolts that secure the plastic remaining to ... something. I loosened both bolts but it wasnt clear what was now free to move. You can snap off the leather trip that lines the center console. There is a "cap" on each side that simply pulls off by pulling up. Easy. The sides also are on clips; snap of by pulling to each side (outwards). That does give you access to part of the guts of the center console. But not near the lighter. THere's a plastic piece on the center console that is immediately above the rear end of the carpeted area; it faces the front of the car. I figured that would give me access to the lighter. The top rim snaps off, after you remove the leather trim from the sides of the main part of the center console (the part with the cup holders in it). They, too, snap out to each side; it is easiest if the seats are in the farthest forward positions. After removing the sides of the main part of the center console, the top edge of the piece of plastic I referred to above (immediately above the rear end of the carpeted area) snaps out with clips. I figured the bottom would snap off with clips too, but try as I might, no luck. Turns out there are two screws that secure the bottom of that piece of plastic from the back.
So, remove the rear passenger vents (simple clip release on one side; the whole thing comes out). You are left with a plastic duct that comes up from the floor to feed the vent you just removed. The screws you need to loosen are behind that duct. There is NO WAY to get that duct out! I think it must have been grown from embryonic duct cells in place in California. There are 4 plastic retainers that secure the duct to the sides of the center console. Removing those does ... nothing. You can not slip the duct out, so it is really difficult to get to the screws that are behind it. Eventually I was able to bend the duct slightly (pliable plastic) and slip my torx screwdriver behind it to loosen the two screws, and VOILA, the plastic piece on the front of main part of the center console falls off.
Did that allow me to get to the wires feeding the cigarette lighter? NO! I could reach the wires with my fingers, but I could not get access to them to tap into them.
Go to the fuse box. You remove the "service" panel which is the plastic cowling at the back of the frunk, abutting the windshield. Snap it up from the windshield edge, then pull it back towards the windshield. You need access here anyway if you ever want to check fuses, or check brake fluid. There are two accessible fuse boxes (and one that is not so accessible). The key for the fuses is in the Owners Quick Guide. I chose the fuse that is for the "12v power socket." This is a 15A fuse.
You have to remove the back of the fuse box. To do this, remove the fuse box with 2 10mm bolts; turn it upside down. There are 4 clips that hold on the back (bottom) of the fuse box. Release them with a small flat screwdriver inserted from the TOP side of the fuse box. I wish there was a way to "disconnect the negative terminal of the battery" like you do on all ICE cars when doing any electrical service. You can turn the car off from the touch screen, but it automatically turns itself on again at random intervals (annoying); even with it turned off you have not de-powered the whole car. So just BE CAREFUL. (If someone knows how to truly power down the whole car for service, please tell me!). The fuse in question is FED with a large white wire, and the output of the fuse is a smaller white/black wire. It is fuse F35 (see diagram on page 27 of your manual) You want to tap into the smaller white/black wire that you can see attaches to the fuse in question. Remove the fuse first. Carefully strip 1/8" of insulation, attach your wire, and tape it carefully. When done, make sure the end of the wire you just attached is not contacting anything important, then replace the fuse. Now you should be able to measure 12V (or maybe 13V) between that wire and ground when the car is on, and 0 (or a few mV) when the car is off.
For the ground, I simply attached a fitting to the bolt that secures the lift for the frunk.
What an adventure!
Let me know if you have any additional tips! (but my work is done...)
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