OBC mystery plug.

Tue Mar 31, 2015 10:43 pm

Fitted last weekend a complete Obc but seem to have one plug left over that i can't account for. Its on the lower loom and seems to be the engine side of the bulk head. Going by the short lenght of cable it fits to something just under or around the fuse box. But theres nothing like that to plug into. Is it just not used, any ideas?

Tue Mar 31, 2015 10:49 pm

There should be another unused plug just the cabin side of the bulkhead, with a brown/green wire running between the two. The other pin in the engine side plug is earth, and on the inside one, is 12 volts+, so one side is a switch controlling something on the other, but I have no idea what. I've never seen anything connected to them.

Tue Mar 31, 2015 11:11 pm

Possibly a contact switch by the rear bonnet runner to go with the alarm?

Ben

Tue Mar 31, 2015 11:18 pm

BenHar wrote:Possibly a contact switch by the rear bonnet runner to go with the alarm?

Ben

That would make sense if the wire anywhere, but it's a stand alone simple circuit consisting of wiring for a switch and the switched, only a few inches apart, but on different sides of the engine bulkhead.

Tue Mar 31, 2015 11:19 pm

It must go engine side because the grommet that goes in the bulkhead won't slide over it. Maybe its for another model. Everything seems to work.

Tue Mar 31, 2015 11:36 pm

There's another similar unused plug inside the car - between the grommet, and where the loom branches to the earth stud, accessories socket and immobiliser socket.

Wed Apr 01, 2015 11:50 am

Brianmoooore wrote:
BenHar wrote:Possibly a contact switch by the rear bonnet runner to go with the alarm?

Ben
That would make sense if the wire anywhere, but it's a stand alone simple circuit consisting of wiring for a switch and the switched, only a few inches apart, but on different sides of the engine bulkhead.

Maybe if you have the magnetic key alarm the plug inside connects to the loom for that?

I know my cabriolets have this. Picture shows it between the runner and fuse box.

Ben

Wed Apr 01, 2015 5:24 pm

BenHar wrote:
Maybe if you have the magnetic key alarm the plug inside connects to the loom for that?

I know my cabriolets have this. Picture shows it between the runner and fuse box.

Ben

My cabbie came with a switch like that,it was connected to the (non funtioning)BMW dealer-fit alarm system.The loom also went to the pin switch for the boot light.

Wed Apr 01, 2015 7:36 pm

That black plug does indeed go to the bonnet switch for the alarm system with the magnetic key. The 13 button has two wiring looms, one in the bay which is obviously universal to both magnetic alarm cars and non alarm cars and then the dash loom for the OBC.
Cars with the magnetic alarm also have this wired into the OBC's external black unit which is located above the DME.