Central Locking Problem
 

I have bought a 1997 E300 diesel and am really pleased with the car. However, in my haste to find out how all the controls worked I pressed merrily away at all my buttons and gidgmos and for some reason my central locking now doesn't work (it did before). When I press my RC, the 4 way flashers come with a beeping sound for a few seconds with no green or red light under the mirror. When I press it a second time, a flashing green light comes on under the mirror but nothing else happens. I have tried to re-syncrhonize but to no avail. Any ideas?