12v socket - change to switched feed

[darich]

Hi

I recently discovered my 12v socket wasn't working. Checked the fuse, cleaned up the connections and it's now working fine again, although I noticed during the process that it's live with the ignition off.
I had a vague memory of my roadster staying live for a period after switching off the ignition and assumed my coupe was the same.

I bought a 12v DAB radio which uses an FM station and got it all connected up at the weekend.

I noticed this morning that the DAB unit was still on, so the 12v socket isn't timed in any way - it's just permanently live.

Is there any easy way of changing this to a switched supply?

 

[TheDan]

Here is a diagram of the fuse box (for a 2004, but I think it will be the same for the facelift models):



I looked into this a while ago as my battery was draining and I was pretty sure it was the FM transmitter I had plugged into the 12v socket (now changed for just a USB port). I found this on bimmerforum:

I tilted down the fuse box, found and pulled out the 15 amp fuse for the cigarette lighter. Then I made two short cables (~ 2 1/2") each with a 1/4" spade crimp connector on one end and the corresponding female part on the other. The fuse was re-inserted in to the two female ends. Then I put one male end back in to the side of the cigarette fuse socket that went to the cigarette lighter. The other male end went to a close by empty switched circuit +12V (I used the roller blind slot). This work perfectly. I get switched +12V like I want with no modifications to the interior. Also I can, in a minute, put it back to original.

Three quick points.
1) Use a volt meter to make sure you have the right side of each fuse socket.
2) Put some insulation, like heat shrink around the female socket to ensure it does not short to anything.
3) Put a little double sided tape on the fuse so it sticks in there nicely.

An alternate method is to remove the cigarette tray and control module and then unplug the cigarette lighter. Either buy a new 12v socket or cut the wires on the existing one and wire it to a switched fuse on the diagram above (number 2 if its unused on yours or piggyback an existing one).

Be very careful working with electronics and if you're not comfortable, call a professional.

 

[kis]

I’ve added one of these, which replaces the traditional cigarette lighter - who even uses one of those these days?!

Has a little button which lets me turn it on and off, as you say it’s always live/hot.

 

[darich]

Here is a diagram of the fuse box (for a 2004, but I think it will be the same for the facelift models):

2004 BMW Z4 (E85) Color Fuse Diagram.png

I looked into this a while ago as my battery was draining and I was pretty sure it was the FM transmitter I had plugged into the 12v socket (now changed for just a USB port). I found this on bimmerforum:

I tilted down the fuse box, found and pulled out the 15 amp fuse for the cigarette lighter. Then I made two short cables (~ 2 1/2") each with a 1/4" spade crimp connector on one end and the corresponding female part on the other. The fuse was re-inserted in to the two female ends. Then I put one male end back in to the side of the cigarette fuse socket that went to the cigarette lighter. The other male end went to a close by empty switched circuit +12V (I used the roller blind slot). This work perfectly. I get switched +12V like I want with no modifications to the interior. Also I can, in a minute, put it back to original.

Three quick points.
1) Use a volt meter to make sure you have the right side of each fuse socket.
2) Put some insulation, like heat shrink around the female socket to ensure it does not short to anything.
3) Put a little double sided tape on the fuse so it sticks in there nicely.

An alternate method is to remove the cigarette tray and control module and then unplug the cigarette lighter. Either buy a new 12v socket or cut the wires on the existing one and wire it to a switched fuse on the diagram above (number 2 if its unused on yours or piggyback an existing one).

Be very careful working with electronics and if you're not comfortable, call a professional.

Cheers mate.....I get how it's done but I think it would be easier, and less likely that I'd make a mess of it, if I altered the socket.

 

[darich]

I’ve added one of these, which replaces the traditional cigarette lighter - who even uses one of those these days?!

Has a little button which lets me turn it on and off, as you say it’s always live/hot.

Looks ideal.
I bought a plug in version which includes a voltage meter, but I might end up doing this as a more permanent job in the future