Central locking problem

Wed Mar 11, 2015 1:47 pm

Hi,
I have a wee problem with my 96 E36 316 4dr central locking system. It stopped working and at the same time it developed a steady drain on the battery. it would be completely flat after approx 24 hours.
The fuse box has 3 fuses listed for the CLS, two 5 amp and one 25 amp. the 2 smaller ones are fine but the 25 amp one is blown. When changed it blows as soon as you turn the key in the door lock.
Any advice welcome on where to start looking for the fault.
The bit that confuses me is if there is a short somewhere and this has caused the fuse to blow then how come it is still draining the battery. Prior to the locking system failing I never had any problems with the battery. When changing the battery for a charged one you get a spark when connecting the terminal although everything is "off" on the car. It seems to me there is a short somewhere but Im not sure where this is likely to be.......

Wed Mar 11, 2015 2:18 pm

The lock motors used on BMWs of this era (including the last of the E30s) are notoriously unreliable, with the microswitch that indicates the position of the motor becoming detached from the motor itself. This could lead to the motor being powered when it's already at the limit of its travel, and unable to move, which would cause an overload, but I wouldn't think it would quickly blow the 25A fuse, which is more there for short circuit protection.
Is this any use to you: http://www.autolib.diakom.ru/CAR/BMW/19 ... S/2269.pdf I can't guarantee it's completely accurate, so check what you have matches up.

Wed Mar 11, 2015 2:43 pm

Thanks for the quick reply Brian, The wiring diagram looks accurate enough to help understand the circuits involved, but to be honest I'm not that bothered about the system actually working as I'm quite happy to open the drivers door manually with the key and pull up the buttons on the other doors when required. I only use the car as a work runaround and its a low value car. The constant drain on the battery is more worrying, due to fire risk etc, and I have resorted to disconnecting the battery when leaving the car for more than a few hours. So if I can work out where the current is going and stop that I will be a happy man. Any Ideas ?

Sat Mar 14, 2015 10:32 pm

A common fault on these is the boot loom where it comes out the body and into the boot lid.pull the grommets out of the boot and body and peel back the the covering and see if any wires are broken and shorting.

Mon Mar 16, 2015 9:04 am

Thanks wellard, I stripped out the drivers door lock, and plug, could not see anything untoward, put it all back together and the CLS is working fine now...... Tried it this morning and the battery has held its charge since Saturday, so fingers crossed its ok now.
I will check out the boot wiring as well though, thanks
Jim