Locking system not working when cold outside

[youngbimmer]

Today I went to lock my 735 as I got out of it to go inside to work, found the locking system completely unresponsive from both front doors and the trunk. Trunk manual lock will engage for only the trunk. It is below 0C outside but I did not expect this to affect the locking system. Anybody run into this before?

[Sansouci]

I've never had this problem but heard that if you heat up your key (BIC lighter comes to mind) it will help. I recall that the system may have an internal heater (Shogun?)

[shogun]

Driver side has a heater in most countries, in some it was optional if I remember right, you have to pull the door handle up. But that seems to be an electrical problem. Central locking is done via the GM and RM under the rear seat.
I had problems on one door, but that were broken grommets in the linkages of the door system. https://www.bimmerforums.com/forum/s...light=grommets
You had a lock problem in May this year already https://www.bimmerforums.com/forum/s...light=grommets
Maybe there is moisture in the lock system and now frozen and the old hard grease hardens even more now in the cold weather.

Or the needed power was too high because of frozen locks. The GM has an internal overload relay, so there we are limited with the GM. The relay switches off
when there is > 60 seconds more than 36A or
when there is longer than 0.3 seconds between 36A and 60A (overload)
when there is longer than 0.1 seconds >60A (short circuit)

This internal relay inside the GM is additionally to the normal 30A fuse. The electronic fuse is reversible. Inside the GM the load of the RM is measured and in case that exceeds certain values, the reversible fuse will stop the action. The switch off values are set to less than the 30A fuse. So this 30A fuse will not melt. An automatic switch on comes after 60 seconds, however, only, if the power consumer was switched off or in case there is no short circuit detected. The lock is released by switching off terminal 15. A automatic switch on is possible 6 times with terminal 15 switched on. For example to reduce the Amps only max. 2 window switches can be operated at the same time. In case several window switches are pushed at the same time, only the first 2 pushed ones will operate. In case already with 2 pushed switches the limit is reached, the system will switch off one switch. In such case the front door windows have priority.
See under 10 ZKE German language function description of the GM http://www.e32-schrauber.de/bmw/s-zke.htm

I removed the lock system, cleaned it with Kerosin that the old hardened grease went out and then re-greased it and they work nice, Sean disassembled them completely and drilled out the rivets to clean them http://bmwe32.masscom.net/sean750/do...kMechanism.htm

[youngbimmer]

Yes after I repaired the passenger door locking system, everything was working fine. Only problems started appearing in the very cold weather. I can believe the moisture problem, it’s very hard to open my doors in the winter when there is frost almost like the doors are frozen shut to the chassis. For the passenger door lock actuator, I sprayed it liberally with carb cleaner to remove old grease and the sprayed it with white lithium grease to relube it. Worked fine after, unfortunately now it is too cold to investigate. More spring projects I suppose

[Sansouci]

Youngbimmer,
I've been told that lithium grease is s no-no on lock parts while spray graphic powder is recommended as it doesn't harden nor does it pick up dirt. White lithium is OK for linkages. Also I use gummiflege sparingly on the door gaskets.

[Cactuar]

Which grease should be used inside of the lock mechansim, after the old grease has been removed with solvent please?
I'd like to use a product that won't require re-greasing in the future if possible.

[shogun]

Don't know what is the best, I use moisture and dirt resistant motorcycle chain lube, also has anti-fling formular and keeps the lube exactly where it is needed.

[Cactuar]

That's a good idea, sounds like a good product for this application. Thanks Shogun!