#5. Now here’s a tricky part. We need to route the 12 AWG power supply cable from the battery to the power converter. It’s actually easier to route the cable from the footwell outward to the engine bay. I used the hole in the firewall that accepts the clutch master cylinder and hardline. If you have a manual (I have an auto), I’m guessing you have enough room to push the battery wire though that opening. If you have an automatic, purchase the BMW grommet for that opening. To install it, push out the paperboard perforated cutouts that are blocking the grommet hole and install the factory firewall grommet. Keep in mind there are two firewall openings, one for the clutch master cylinder/hard line and another higher up for the soft clutch fluid supply line. I chose the lower one, but the higher one should work too. See picture below.
Once you push the wire through the grommet, it will probably end up on the far left side of the brake booster. I routed the wire over the brake booster, through the hollow rubber hood seal and to the battery. Crimp the battery wire to the other end of the inline fuse holder.
At this point I removed the dead pedal and routed the battery wire along the already existing bundle of wires. You also need to remove the lower door edge trim panel. Force it backwards to release it from it’s clips. Once that’s away you can pull away the carpeting and route the wire behind it. At this point you will “rejoin” the factory wire bundle near the passenger’s footwell/side panel. Continue to route the battery wire along the factory wire bundle. It’s pretty self explanatory where to route the wire once you get it to the back seat. Finally crimp your battery supply wire to the converter battery wire Here’s some pics...
The wire leading out of the battery box and into the hollow hood seal.
Routing of white battery supply wire
Passing over booster and down towards firewall grommet.
Now inside the cabin looking forwards.
Didn’t get a shot of the dead pedal off, but this is a zoomed-out shot of the last one. The wire runs straight down behind the dead pedal.
Door trim panel removed.
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