525td Remote Central Locking

I recently aquired a 1994 BMW 525td, all the electrics seemed to be working fine when i bought the car. After a few months the remote
Central Locking stopped working. I assumed the battery in the key fob was dead and replaced the battery only to find that it still didn't work. I have also checked that all the fuses in the fuse box are okay.
Does anyone have any ideas on why the remote central locking is not working?
Also on the same day this happened my CD player stopped working, however when i put the original radio cassette player basck in it works fine!! I also know that the CD player works as i have tried it in another car!
Could there be a link between the 2?
Any help would be greatly appreciated.
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