Tapping 12-volt supply

[doogie]

The only real concern is working out what fuse is on it, as if it's a small one you might pop it all the time - looking through Bentley or a pdf wiring diagram you should be able to work it back to where it hits the fuse box.

[ElNormo]

I'm wiring up an XM radio, to sit next to the shifter handle. I've removed the surround, and have found a bundle of wires, one includes a wire that is hot when the engine is running or in "accessory mode".

So the question is... do I go ahead and tap one of these, or do I need to do some research first? I've poured through the schematics in the back of the Bentley manual, but can't match the color wires with anything that makes sense.

I'd rather tap into something innocent like "cd changer" (which doesn't exist), rather than something scary like "central locking".

Suggestions?

Thanks!

Norman Elton

[ElNormo]

looking through Bentley or a pdf wiring diagram you should be able to work it back to where it hits the fuse box.

Thanks for the quick response! So if I know which color it is... where do I begin looking in the manual? I wish there was an index by color.

For instance, I've found the following wires:

WHI/YEL (always on)
YEL/BLU
WHI/BLU
WHI/BLK
BRN/BLK

They're all in a bundle underneath the center console, but when they're disconnected, I can't find anything that isn't working!

Thanks for any advice!

Norman

[Tiger]

Usually the positive switched is red... solid red. That only comes on when ignition is switched on.

Yellow is the constant... which is always on yellow... solid yellow.

Most striped and matching solid wires are speaker wires... and blue is always antenna... switched positive too... sometime BMW is blue with thin white stripe.

Check with voltmeter and you will know for sure.

[doogie]

Basically to trace it back you need to work out what it starts as.... from location it sounds like it's likely to be either connected to the gear electrics, window/ hazard switches, or possibly pre-wiring for ASC/ DSC switches ? If it's got a plug on it then you should be able to work out the plug number by shape and colour and a wiring diag pdf, which should help identify what it is.

(the only other possible concern apart from fuse is if it's a really small gauge wire and the XM has a large power requirement then you might overload it, but it's unlikely!)

[ElNormo]

So using a handy online wiring diagram (http://shark.armchair.mb.ca/~dave/BMW), I've confirmed that the connector I'm looking at is X506. There is also connector X511 nearby, either one would work.

When I disconnect X506, the car starts in "trans program" mode, which leads me to believe something in there is transmission related. I'm a little hesitant to start messing with anything there.

Unfortunately, the PDF is not searchable, and I can't find a way to locate either connector in the schematic, to see how it's fed.

The saga continues, thanks again for your help!

Norman

[Ross]

Post the color and where the bundle goes.
EDIT I see this wire is connected to the trans range switch. I'm suggesting not to use that wire for fear that it may cause trouble with the trans control which seems a sensitive part of these cars.

[doogie]

X511 = automatic transmission range switch , connects to F17 which is 7.5A
X506 = automatic transmission switch (S/E/M) and link to instrument cluster & check control.

The wire on X511 pin 1 which is green/ red should be hot in run or start, which is probably what you want - check that 7.5A is sufficient for your device (and remember that if your device draws close to this then you may get problems popping fuse 17 if it and the transmission try and draw current at the same time)

HTH!