Nissan Serena Central Locking Problem

Hello,

This is the first time I have posted here so if I get it wrong I apologise in advance !!

I have a 1991 Nissan Serena FX which has been imported to the U.K. from Japan, it is a 2ltr turbo diesel automatic with central locking.

The problem I am having is that occasionaly the doors will lock themselves without any input from me, and will also unlock in the same manner. This can happen when driving, or with the vehicle just sitting still, with or without the keys in, or even when left overnight, in other words you can lock it  but it may, or maybe not locked when you next go to it. The only exception to this is  the sliding door, which will lock on the central locking but will not always unlock, this happens about 50% of the time, has anyone else had this problem?

Also can anyone tell me where I can obtain the wiring diagram's for the central locking system please.

Many thanks for reading this, best regards to all, John.

I would be looking for a "short" or bad switch...there is NO info on this car anywhere I can look. DEI has a 93, but no 91 and thats it!

I would ask a dealer (nissan) if there is a module under the dash that controls the lock system

Many thanks for taking the time to read and reply, I have tried all over like you to get info and/or wireing diagrams,but all to no avail.

I think there is a short circuit to earth somewhere, at least I hope it is to earth and that the locking system is   negatively switched, if not I would have thought I would have fuses blowing all the time, but they are ok .

I have been in touch with my local Nissan dealers workshop manager,( who I had as my apprentice many years ago!!! ) but he is unable to help either, again, no info available.

If I have any luck fixing it before someone sees this post  and can tell me anything about the problem I will let you all know what the trouble was, in case someone else has a similar problem.

Best regards, John.