Herratic behaviour of central locking system + windows

[MadMax]

Hello there, I have lots of problems with central locking on my 318 convertible (yr 95).
It all started with a flat battery one morning I could not explain. After jump starting it was obvious that something was wrong with the central locking closing herratically and windows only working at times. I tried disconnecting the battery in order to reset the system but it did not change a thing.
Removed then fuses 7, 35, 43 and disabled central locking + windows for a couple of weeks.
During this period the battery gained strength and was back to normal. After 15 day and reconnecting the fuses the whole system was ok for a day or two then started to play up again, the battery is suffering and now the radio system for the central locking isn't opening or shutting at all.
I am not sure where to start to find the fault. I guess I could just change the central locking unit but I would rather have a more precise idea of what I am doing before just trying to change components................can anybody help with this one ??

I would be very grateful for some ideas on how to diagnose the fault.

[jitsjaf2009]

Get the battery tested, instead of it being the victim, it may be the problem. It shouldn't take several days for an alternator to "rebuild" the battery. If it is not a bad cell in the battery, check the alternator. Before going to autoparts store for a check, take a multimeter on DC volts and test (1) the battery static, with everything off. Should be be 12+ volts. Now start the vehicle with (2) everything turned off (yes...even your radio). Should see 13.5 to 14.5 volts. Now turn on headlights, radio, heater fan and test again. May dip momentarily, but should stabilize at same reading before you turned everything on. If these are not pretty much right on you have either a battery problem or alternator. If you disconnect the battery and car continues to run and volts are between 13.5 and 14.5...it is the battery. Many newer cars will not run with battery disconnected. Our BMW's get real squirrely with low voltage!

[MadMax]

Thank you for your reply.
Yes, I did think of the battery and replaced it with a different one, normally on board of my 523, for the purpose of a test. Nothing changed unfortunately.

I am currently investigating the central lock/alarm remote control which may have had a low battery. At the moment I only have the central locking on (alarm disabled by key) and the herratic behaviour seems to have stopped. I suspect that when the remote control does not have sufficient power may transmit spurious signals able to confuse the receiving equipment on board of the 318. At the moment it seems to work ok (have not enable the alarm yet) if I just use the central locking .
Anybody have any experience about having a low battery inside the open/close remote control ?

[jitsjaf2009]

I just change the battery...The owner's manual has a procedure to "resync" it to your vehicle if batter is dead or out of remote too long.

[MadMax]

Ok, time for an update. It is October now and the problem reappears after a quite summer of perfect work. The fault was evident before the heat of the italian summer, stopped for 3 or 4 months then reappeared again. About 3 weeks ago, for justa couple of days, we had the first temperature drop of the season and the fault manifested itself and then disappeared again with the rise of the temperature until yesterday when we had another proper day of autumn.
Now I know it is connected to either low temperature or excessive humidity.

My 95 e36 has a central locking/windows unit which is driven both by door sensors or alarm central unit so I disconnected the alarm unit to see if this unit could possibly be responsible for generating spurious signals which, in turn, would not drive the Central Lock Unit properly and telling it to lock doors when it shouldn't. A few minutes of driving and the problem recourred again so it looks like it is not the Alarm unit to malfunction.

Ok, so what do I do now ? I have come to the conclusion that the doors shut herratically either because of a mulfunction of the Central Locking Unit or because of a problem in the feedback i.e. door microswitch. A possible scenery could be depicted as follows: the microswitch in one of the two doors has become defective and, because of humidity, herratically signals a "locked state" to which the CLU reacts by locking both doors (the same way as it would happen if you used a key to lock doors; when you put the key in the lock and turn it to lock then a signal is rightfully sent to the CLU to active door locking motors but what happens if that signal is sent as a result of a mistake ?).

I am thinking of disconnecting both door microswitches and temporarily use the alarm button to lock/unlock the doors in order to see if spurious signals might come from the microswitches. If I do this I will not be able to lock/unlock doors by using key but it does not really matter as the alarm wil do the job anyway. If the herratic behaviour continues then I know that it is not the door microswitches and I will look into the CLU.

Opinions would be very welcome !! Thanks in advance !

[jitsjaf2009]

This helped me with a similar problem...where is VMZ when you need him???
by VMZ on Thu Sep 06, 2012 2:26 am

If your windows are still down and you have one touch, you should be able to insert your key in the door lock, turn it towards lock and hold. Windows and roof should close if they are open.

Which fuses did you check? Double check 11, 14, and 43. 43 has nothing to do with windows but has been known to effect them.

Your comfort relay is under the the dash on the drivers side. There's 5 relays, 4 in a square and one off the side. The odd one out is the comfort relay.
Page 610-2 in the Bentley manual(the only E36 manual worth having)

I truly wish you luck...tonight I will spend some "quality" time with my Bentley manual and see if I can find anything more.

[MadMax]

jitsjaf2009,

thank you for your opinion but I am not sure I understand what you are trying to suggest.
Is related to what I wrote above in my last post ?
Thank you for your kindness, it is very much appreciated !

MadMax

[MadMax]

UPDATE 16/02/2014

Ok, I tried inserting a new microswitched motor first on the left side (no joy) and then on the right side (again no joy !!!) so I have wasted 92 € just to do this test !

The behaviour of the central locks became so herratic lately that I decided to disable them by removing fuse 35; after doing that things went even worse and windows were often going up and down completely on their own, at times they would stop functioning completely.......I kept the system going without the 35 fuse for a couple of days and then decided to put back into place because I reckoned it would be better to have an herratic behaviour of the central locking system rather than having a mad mad behaviour of the windows.

SURPRISE: when I put the 35 fuse back in the fusebox the central locking system came back to life and started working fine. It has now been ok for a couple of days but I doubt that it will last........waiting for the next sign of mulfunctioning which, by the way, seems to show more on very wet rainy days.

Has anybody got an idea of what might be happening to my car ?? Even professional mechanics don't seem to know what is going on, they just tell me to try this and that but all those tests simply involve substituting parts ........so not much of great help really !!!

Please, any help/hint would be more than appreciated.

[jitsjaf2009]

Removing the fuse probably allowed the module to reset to factory default and dump any extemporaneous inputs. It is one of the reasons many having problems with programmed modules will disconnect the battery for an hour and reconnect. Just make sure you have the radio code if you do this.

[MadMax]

UPDATE 18/03/2014
Ok, time for another update:
As I said in the post above, after reconnecting fuse 35 the central locking had been working fine for a couple of days. After that the system was working nearly ok with minor faults like windows staying slightly open when the SHUT command was given bu no major issues like herratic openings or shutting. At one point, I noticed that the radio control button was not working at all so I opened it to see what was wrong with it; the usual oxid on the battery contacts was stopping the module from working. it was at this point that I noticed that one of the remote control button plastic hinges had come apart from the main lobe of the button and not being all one piece with the button it was stopping it from moving in a completly free manner. Considering that this little plastic hinge, come apart form the main button, was not essential to operate the button I decided to remove it. As a result of that the button felt different to press and its movement was more definite and less impeded. Since then all problems seem to have gone (about 20 days of perfest functioning now). It is true that the season is better now and humidity has gone down a lot but I have the feeling that that could be it. May be the dodgy way the button was pressed caused spurious signals to be sent to the receiving station which in turn would go crazy and drive the locks in a mad fashion. I am keeping it under observation for now but no fault whatsoever. If the problem really depends on humidity it will show again in autumn. Will keep you posted if I have any news on this strange matter.