Central locking will not lock nearside rear door

[Farleyjim]

I have just discovered that my nearside rear door does not lock when the central locking system is operated. All other doors and tailgate (A4 Avant 1.8T) are OK. I noticed this when the red LED on the driver's door remained on after the initial flashing. Does this sound like a sensor or switch in the rear door being faulty? I'm not sure whether the system is operated by a vacuum pump or not, but I am prepared to take off the door panel to investigate the fault. I would welcome any clues or tips from anybody who has a theory about the problem. Many thanks.

 

[variosso]

Have you checked if VAG COM throws any faults?

 

[Farleyjim]

I'm afraid I don't possess VAG COM but I think I am a reasonable DIY person. I just wondered whether anybody had had any previous experience of my problem.

 

[Paul Messenger]

Only in the last 24 hrs has my 2010 S4 Avant developed a fault in the nearside rear door central locking. However, on mine it locks but won't unlock. You can hear the solenoid clicking on both functions when the door is open but no solenoid noise when shut.