I've got a 96 C280 and the locks are giving me grief. The nitty-gritty:

The IR remote stopped 'working' (i.e. unlocking the doors), although the red 'indicator' flashes. After resynching according to the procedures outlined in the manual (press button remote twice then turn key to position #2) failed to fix the issue, I replaced the IR remote's batteries and resynched. Still non-op.

Next I checked the fuses - starting w/fuse #23 (the buse box indicates that fure controls the dome light, rear headrest down feature and remote IR system). Fuse was fine. Dome works OK. But, the rear headrests don't fold down when the button is pressed - although there is a clicking sound eminating from back near the headrests. I proceeded to check all the fuses - hood & trunk mounted - and they are all OK. Not sure if the headrests are the same or a different problem.

SO???? What could the problem with the IR remote be if it's not the batteries in the remote nor the fuse?

Thanks for the advice!