Central locking problem

[saspedor]

When trying to unlock/lock my 1995 SL500 using the remote nothing happens.
The key locks/unlocks the car when used manually (vacuum is ok).
I have synchronized the keys to the car.
The remote arms/disarms the car when pointed at the door or mirror (red or green light come on).
Checked the module next to the Vacuum pump in the trunk for loose connections all ok.
I have changed all the fuses.
I don't know what to do next to identify the problem,
Please help!!