I recently replaced drivers side door switch for a drivers side window problem, ( not rolling down or up properly), but now the problem has started again. In addition, the rear liftgate door will not unlock at all, not even by using a key. Every time the other doors lock or unlock, the rear door makes a buzzing or humming sound and fails to unlock. Any help would be wonderful.

Hi
I am not sure why your liftgate will not even unlock with the key, however the buzzing when you hit the power lock is likely the actuator spinning. When I changed mine out on my '96 I was able to see that the sound was the plastic gears spinning on each other due to wear. You probably need to replace that actuator, but first you will need to free up the lock mechanism.