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I used an add a circuit on the 25A(I think?) next to the two 15A fuses on the front passenger side of the engene bay fuse box. It's unused you can find it on the fuse chart.
So I ended up using that 25A fuse, but I can't figure out why that fuse had power on it with the key off when I put the multimeter across it... it's just not adding up.
Which fuse are you using in the photo below? If you are tapping into one of either fuse 54 or 53 and use the far left (passenger side) socket you will get +12v acc power (only on with ignition). If you use one of the far right (driver's side) sockets in those fuses, you'll get +12v constant. To get ign from one of those fuses you'll either need to move the fuse to the right orientation and use a male spade terminal on the left socket, or you'll need to use a fuse tap and make sure it's on the far left socket and fuse blade.
Which fuse are you using in the photo below? If you are tapping into one of either fuse 54 or 53 and use the far left (passenger side) socket you will get +12v acc power (only on with ignition). If you use one of the far right (driver's side) sockets in those fuses, you'll get +12v constant. To get ign from one of those fuses you'll either need to move the fuse to the right orientation and use a male spade terminal on the left socket, or you'll need to use a fuse tap and make sure it's on the far left socket and fuse blade.
I used the one that says 25 on it, I used an add a fuse kit, 12 gauge wire, crimping tool, and these WAGO terminals to join all the wires together. I'll snap some photos of the set up.
My fuse diagram shows that you used fuse 57 which is listed for CDI control unit for engines 646, 647, 648. I have a 04 E55 and I just now tested fuse 57 and I don't get any volt reading with the car off or on. I would suggest you move your add-a-fuse to fuse 54 cigarette above and make sure that it is in the far left position (towards passenger side of car).
My fuse diagram shows that you used fuse 57 which is listed for CDI control unit for engines 646, 647, 648. I have a 04 E55 and I just now tested fuse 57 and I don't get any volt reading with the car off or on. I would suggest you move your add-a-fuse to fuse 54 cigarette above and make sure that it is in the far left position (towards passenger side of car).
The 25A is unused, keyed power, and I have been using it for over a year for both my methonal pump(with an Led indicator in the cab during operation) and one of my intercooler pumps.
There must be differences then on some model year E55s and/or as equipped for that fuse 57. I have the 25amp fuse but no power in any ign circumstance.