The pax side door lock sometimes releases and it can be open from the outside, other times it does not releases and door can't be opened fro outside. Is there any simple solution or I need to change the lock system on door.

 

would be helpful to know

1) year
2) model
3) country
4) using remote key or central locking button on dash

 

it's a 1999 E 320, Puerto rico

 

Using remote key

 

it doesn't sound as though it is the locking mechanism that is failing here. i could try and
check the pneumatic line leading from the PSE pump (under the rear seat, next to battery)
and leading to the right side, front door. the lines are plastic and may have a leak, or frac-
tured connection at one of the T-fittings.

i don't know why all the other doors would be functioning okay, but only the right front door
is sporadic in operation unless it was the pressure line.

hard to guess over the keyboard unless one was there to try different ideas and isolate (and
rule out) what does/doesn't work each step during troubleshooting.

the diagram is what I've determined to be the pin-out for the PSE pump for my 1999 E320 sedan