The BC1 (Body Control Unit) is in the drivers side (UK-RHD) footwell of the 2001-2006 R50/52/53 MINI's, it controls many electrical items and can send many things haywire if even a drip of water gets into its pcb connectors until it dries out. If you pull the footwell bonnet catch lever, hold it open & shine in a torch behind the trim panel you will see the top 2 multiway connectors to the BC1 or a black plastic cover. Early MINI's (pre 2003 approx) did not have the black plastic shield over the connectors to protect them from any small drips of water running down cable harness inside the windscreen pillar. Later cars do, my 2002 Mini only had a piece of clear plastic film draped over the connectors (a factory or dealer stop gap fix I guess) and was randomly locking / unlocking the central locking by itself after any rain / wet weather, washing the car, etc. I removed the inner sill plastic trim panel & fitted the later water shield cover (part no.61356942512 approx. £2) over the 2 top connector plugs. See Diagram Item 9:- http://www.realoem.com/bmw/showparts...00&hg=61&fg=25
If this is the problem do not ignore as long term corrosion inside the BC1 means a new unit.....very expensive outside warranty. (Some people have successfully opened more badly water damaged units, dried them out gently with a hairdryer, removed any corrosion and got them working again).
Below is the BC1 connections listing showing how many things it communicates with and is also a useful reference. Connections may vary a little depending on the options fitted and the year of your MINI - always double check with the Bentley/Haynes MINI Manual wiring diagrams or BMW MINI WDS CD or online here: http://www.bmw-planet.com/diagrams/release/en/index.htm
(If the BC1 is replaced with a new or secondhand unit it would normally need to be re-programmed by a BMW dealer.)
MINI BC1 Connections List
Connectors: X332 20 pin (green) "A" X253 54 pin (black) "B" X254 54 pin (natural) "C" X255 54 pin (blue) "D"
Full Connections Listing here:http://forum.minicooper.org/showthread.php?t=9924
Once BMW had discovered the fault originally, all cars (early 2002) made had plastic water resistant film placed over the BC1 plugs while the new cover was being designed, which took a matter of only a couple of weeks. Many of the original cars have unprotected BC1's, but this cover was intended as a precaution rather than a cure. The actual cure was to make sure that A post finishers were fitted correctly, ensuring the clips fitted water tight. Only cars that had ill fitted A post finishers in the first place were affected or badly replaced trims/windscreens later. It was a run of these that caused the original problems. Anyone with an early car that has had no problems would indicate that the A post finisher was obviously fitted correctly preventing water getting behind the green clips.
To access the BC1 Unit: Pull off the rubber door seal (drivers side UK) along the lower sill / doorstep, then carefully prise away the plastic trim panel along the inner sill / front footwell trim with a large scewdriver / rag to protect paintwork. In the interior photo you can see the large round white nylon clips in the bodywork which hold the trim. If you wish to completely remove the trim some find it easier to remove the seat and lower belt mounting. (I normally manage to gain enough access without though).
Reconditioned Exchange BC1 (Body Control Module) are now available from BBA-Reman for a lot less than a new replacement unit from BMW. See Link: http://www.bba-reman.com/catalogue/D...edProduct=1414