Hey guys, I'm having issues with my locks. I've tried scouring the forums and YouTube but can't find anything similar. 2005 MCS (R53)

Heres what's going on:
My key will lock the doors, but not unlock. I can still hear the sound like it's unlocking, but it doesnt actually unlock.
The door lock switch inside makes a sound when it's trying to unlock, but again won't actually unlock. But when I try to use the switch to lock it doesn't even make a noise.
Unlocking the drivers side with the key physically works, as well as using the inside door handles to unlock the doors.

Fuses are all good. I'm guessing the key battery is still good because it still locks the car and there's an issue with the physical switch as well. Anyone have any similar issues or solutions before I go out and tear apart my doors to check the actuators? It's been like this since I bought the car (3rd owner, knew the previous owner, well maintained and only 87k miles) but I'm not sure if it's the actuators either since they're both not working.

Any help is appreciated!

 

Also the key remote WILL unlock the gas cap lock when I use the unlock button, and the trunk still opens with the key remote, furthering me to believe it's not the key battery.

 

Definitely bad door lock actuators. It's a common problem on R53s. There are actually two tiny motors in each actuator - one to lock and one to unlock. The unlock motor has to defy gravity and when it gets weak it stops working. There's a How-To repair section at the top of this site that contains information on how to repair it though it's pretty complicated. Unfortunately, new actuators are in the $200-$250 range. Don't buy a used one because you're just buying someone else's problem and it's not a long-term solution. And, later year model actuators that are substantially cheaper for some reason will not fit.

 

Seconded on bad door lock actuators. Sounds just like when one went bad in my R53.

I didn't think the replacement was terribly tricky, and I don't remember the cost being astronomical, though this was like 15 years ago at this point.