Central Locking Problem

the central locking on my 89 e30 316 has stopped working. it was working fine and then it would work every second time and then every so often and then a month ago it just stopped working, of course leaving the fuel cap locked and me with an empty tank, but i was able to open with the aid of the screwdriver from the tool kit without doing any damage. does any one have any idea what the problem is and where is the central locking unit located? i think its in the drivers door but i havn't checked yet.:cool:

Dont know if this helps. Had same problem. spoke to BMW who told me to look under passenger side carpet. There are connector blocks there that if they get wet ie leak. they corrode. they need to be cleaned up with small file, before refitting. Have been told this is a common fault and place to look for this type of problem. Can also cause some doors to lock while others stay open !!

Hope this helps