Thank you for your reply. I have tried many times with the key locking and unlocking the door, and (when the pump is working) it worked everytime. I am fairing sure that the door switch is okay. There doesn't seem to be any leak in the system as all the locks operated very quickly. I think, for some reasons, the pump is working intermitently. Anyway, I found a good deal on a new pump so I am crossing my fingers that it will solve the problem.

Thanks.