Why do I have to slam the door to unlock the other doors?

Mine is a 2000 ford focus, has no remote key thingy. When I unlock the driver's door the rest of the doors won't unlock unless I slam the driver's door hard, sometimes I have to do it a couple of times. This happens especially in damp / humid or cold weather. Help? :| I don't wanna keep slamming the door to my poor ford focus.

I'm guessing you have a loose/bad connection or wire. Slamming the door hard allows whatever it is to make enough contact for the circuit from the driver's door switch to complete and allow the other doors to lock. Shutting it gently does not.

Get a mechanic to check the switch module and the connections at the driver's door.