Thread: BMW Ignition wire

Where did you check the wire ?

I checked it first in the boot (where its extended to) but when I was getting no voltage, I tested it in the dashboard.

Still no joy.

Not sure what could have happenned as it definately worked previously.
Thanks,
Paul.

fuse?

where is the wire coming from?

I had an E39 and the battery was in the boot. My E31 battery is also in the boot. Is it the same for the E46?

Yeah, the battery is in the boot. I was hoping it would be a fuse but I am not sure which one... i may have to just pull each one out and check it.

Its really bugging me, I dont want to use the switched line from my cigar lighter.

you shoudln't need to. there are some relays there at the back. some that are on when you put the first ign on (the one you want) and some that switch on when the second notch is on (with the rest of the engine). If you get someone to turn key to position 1, then off, and you sit in the boot, then you should hear it. Put your finger on the case to feel the strongest click, and you know which one you need to branch off.

that's how I did it with my E39 anyhow.

The other thing is, whilst on the subject of power and BMW's. You car will switch off the lights inside the cabin off, after 15mins of no activity. This power is restored when you use your keyfob to open/close the door, or any activity. It's almost like a scrensaver!

it's very useful for carpc's in 2 ways.

1) you can have it power up your pc before you enter, and poweroff 15 mins after you leave it.

2) use the power as you currently do, but also attach the cabin light weire to a relay, which powers the entire system. So if you leave your car and for some reason the pc stays on, then after 15mns everything will be shut off, no matter what. (this is how I had it, safest way - I did get a few flats you see!)

Paul, I have an E46 and tapped into an ignition wire which I found in the boot on the left and top. I believe it was purple/white wire. My set up is a couple of years old. Power supply is using an ITPS board and tank battery. It works but was having problems. It might have been my wiring setup. The original setup was just straight 12V from the tank battery. On the 12V to power on the PC I tapped into the same always on 12V and connected it to a switch. I then connected this same 12V (on the off side of the switch) to the ignition 12V on wire. The PC would work most of the time. After a while while driving the car noticed that PC would boot on the power off. Nothing wrong with PC. I just disconnected 12V ignition on wire and it seemed to fix my problems. I was thinking now about maybe connected the 12V ignition on to a relay so that it wasn't directly connected.

What wire are you checking for 12V ignition on?

In BMW ACC comes only to the stereo in the dash.
It does not go into trunk as all devices use IBus for such communication and device should be smart enough to shut itself after bus is silent for some time.
If you have older stereo with round pins the ACC is pin 5 for flat pins 16.
Good luck.

sama, any particular keywords (such as dimmer switch) or something I can use to research that particular line to tap into?

I think that's a great idea and I would like to incorporate that for the power as you suggest -- but certainly need to know which/how to find it.

Thanks.

It turned out to be the fuse for my stereo (this is where I have wired my ACC from directly into the boot).

Once i replaced the fuse.... it worked!!! Excecllent. :-)

CarPC is almost complete....
thanks for the help guys.