Air central locking problem
 

Can any one help me??? I have a mercedes 320SL and the central locking on the front doors does not work, but all the other parts still lock ie the boot and petrol cap. i have traced a problem to the valve that sits under the front seats after by-passing it the motors work. does anyone know why these valves would shut and anyway to re-open them as they must be there for a reason! Any info would be much appreciated!