One of the rear doors on my 2006 Audi A3 keeps setting itself to child's lock, so the door remains unlocked on the outside. What should I do?

Could be Child safety lock help prevent the rear doors from being opened accidentally. The child safety lock levers are located on the edge of the rear doors.

look for the child safety locking device on the inside --usually a small lever near the lock striker

There is also a safety control on driver's side door switch panel; (besides safety lock on the rear door itself).

It on the backside of the door in the jam. A small slot in the door with a plastic switch. move it up or down to unlock or lock.

Hi, check if the child lock is set on. Some cars will have a child lock on the rear doors to prevent the kids from opening the door on the inside. On some models electric door lock maybe at fault.
Good luck.

Child Locks will stop anyone on the inside of the car from opening the door. If the child lock is on then the door can only be opened from the outside of the car. Of course the main door lock must be off just as any door must be unlocked to be opened from the outside.

Now if you do not want the child door lock to be on then you must first open the door from the outside with the main lock open or unlocked. Look at the space that is covered when the door is closed. There you will see the lever that turns the child lock on or off. Simply move it to the off position.

Good Luck.

I have the same car, same problem. I've still not been able to fix it, despite taking the inside panels off the rear doors, checking the rods were seated, applying WD-40 to the lock mechanisms, and manually working the mechanism. Child locks are not engaged, but I tried putting them on and off too. Just won't open.

does it open from the outside if you unlock the door,
if it does the child lock lever is on,open door and on the latch side of the door is a little lever that you can move to make it child proof or not

drivers door lock needs replacing,if you have the central electronics checked it will give you a code,and i will possibley be that door,the microswitches play up in them quite a common fault

time to take it to a shop, you need a new power window motor regulator :(