There must be a reciever in the car somewhere, I think I would try and find out more about that first. It might just be something that can be rectified with vcds/vagcom. Someone will be able to shed more light.
On some models you have to sync the keys to the car if you have replaced the battery in the key or if you have had the cars battery disconnected in order for remote locking to works again. Ive also heard some people had their keys loose sync without having disconnected the battery. It should be in your manual.
On My 2007 Audi A4 i get inside the car and close all doors, press unlock on the remote. Then put the key in the ignition lock. Turn ignition on then off. Remove key from ignition lock. Then press unlock once, then lock. Then its synced.
I know this thread is old, but I come across it when I have same problem, my car is 2005.5 diesel, the remote just gave up to lock/unlock the door, the red light is flashing whenever any remote button is pressed, but nothing happened, then I performed what Wizzman said above, still nothing (I have disconnected the batery for 1hr) and with the last effort I use the key to lock the driver side door manually, then the chrip sounds hear clearly.. Yeath Thanks Wizzman for the direction, take care everyone.
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