how can I fix my focus central locking?

I have a 1999 ford focus.I changed the fuse to the central locking(when I finally found it).Now the doors will not lock with the key fob.When I use the fob the locks close and open straight away.The only way to lock the car is by using the key in the drivers door.The fob works the tailgate sometimes but not all the time.The alarm that I have on the car works the same as the key fob in that the locks close and then open straight away.Please can someone help me.I have also tried to reprogram the fob but nothing works-I hear no chime that everyone keeps on about