Turn off 12v Plugs on the BMW E39 when engines off?

m4cc45 · 8 Jul 2007 at 09:03

Hi,

On the BMW you have two 12v cigarette lighter PSU's (one in the front and one in the back).

I'm looking to get a bluetooth gps and wanted to wire it in so that it is connected to the power all the time. However, unlike different cars, I believe the power on a BMW is on all the time.

I wondered if there was some sort of device I could get so that it only turns on with engine startup?

Cheers,

M.

Usel · 8 Jul 2007 at 10:00

Have seen some people position and wire them up in the glove box. They wire the GPS into the 12v line of the glove box light and it powers up when you open the glove box.

No idea if it would be suitable in your car to have the GPS positioned in the glove box though and the door may get in the way of passengers.

paradigm · 8 Jul 2007 at 10:45

You'd need to replace the live (+12v) line that feeds the cig lighter with the switched live rather than the constant live (both will be fed to the HU somewhere). That way, you only get power to the socket when the ignition barrel is turned with the key (ok so not quite only on when the engine is running, but close enough).

Scania · 8 Jul 2007 at 12:30

The 12v power to my cigarette lighter socket in my e38 powers down as I lock the car, it stays on if the car remains unlocked!

(I've only noticed this after leaving my phone in the car to charge, only to find its not charged on my return.)

Why I don't know! - My dads e39's sockets stay powered constantly, as did my e36 and my mums e46 and my mates e30! :confused:

Amps · 8 Jul 2007 at 12:37

How often are you going to use the reciever ?

My Holux reciever lasts for just under a month when not in use and when it is in use i get several days worth of use.

My point is does it really have to be hard wired?

m4cc45 · 8 Jul 2007 at 17:32

R124/LA420 said:
The 12v power to my cigarette lighter socket in my e38 powers down as I lock the car, it stays on if the car remains unlocked!

(I've only noticed this after leaving my phone in the car to charge, only to find its not charged on my return.)

Why I don't know! - My dads e39's sockets stay powered constantly, as did my e36 and my mums e46 and my mates e30!

I haven't actually tried that - only removing the key - will try that now..

It's actually also going to be fitted in the boot with the item being placed on the parcel shelf. And that's the only reason it's going to be on all the time - it would be a nightmare to switch off and on!

M.

Redrum · 8 Jul 2007 at 18:11

m4cc45 said:
I wondered if there was some sort of device I could get so that it only turns on with engine startup?

As said, you can just use a power line within the car that is already switched on and off with the ignition, like the switched live to the head unit. Alternatively, if you do want to use the power from the cigarette lighter, you can use a relay combined with something else that is switched, like the remote amplifier turn on lead from the head unit. Just make sure theres actually enough power available from what ever you splice into, as you don’t want to overload anything.