Audi Repair: Remote door locks, door locks, factory option

Question
QUESTION: I have a 1993 Audi 90CS Quattro, 220k kms. Since about 2003, the remote door locks donèt work. The button just does nothing. The power locks work when the key is used, though. Any advice is apprecaited. Thanks.

ANSWER: Do you have one or two remote keys?  If only one, then perhaps the battery in the remote key may have failed.  If you have two and both do not function anymore, then the power door lock module itself may have a problem.  Let me know,  Jan

---------- FOLLOW-UP ----------

QUESTION: Thank you for your prompt response. I tried replacing the batteries in the one remote I have, to no avail.
I should point out, however, that the car was once broken into. The ignition was damaged, and replaced. As such, the key used to enter the car is different from the one to start it. The former is any key, whilst the latter is only the key with the little light in it. I was told that the system stopped working after that--which leads me to believe that the control module may have been damaged.
Thanks,
Mathieu

ANSWER: If the ignition switch was replaced with the correct unit, then this should not affect the functionality of the power door locks.  The remote part of the door locking system may be bad, or perhaps there is a fuse which is blown?  Chekc the fuses and I will have a look for extra information on there the different modules are.  Let me know,  Jan

---------- FOLLOW-UP ----------

QUESTION: Thanks again,I really do appreciate.
I checked the fuses, and they were fine. I really have no idea. As a side note: the inside lights do not turn on when the door is opened, which may or may not be linked.
Thank you,
Mats

Answer
Do the interior lights not work on any door, or is just the driver's door non functional?  If it is just the driver's door then it is probably a switch in the door, if it is all of them then maybe the switch on the interior light is set to off, rather than door.  Does it switch on manually?

The remote door locks, was this a factory option or part of an aftermarket alarm system?  If it is an aftermarket system I would check the connections from the alarm and check if the voltage supplied into the system by the aftermarket unit is correct.
Let me know, Jan