1991, 300CE with electrical problems: MAT (Omega) alarm system - old, after market installation.

Can anyone tell me what relay / fuse or other device can affect remote/ keyless entry and possibly (send voltage to radio when key is turned off.)

Which relay and where is it hidden, if that is the cure?

All the fuses located under the hood are OK. But, I can not tell what (after market?) hidden relay may be tied to the radio and affecting both of these symptoms.

Symptoms: Radio stays (on) with iginition key off, and remote (keyless) door lock works sporatically, only to lock the doors.

The Mercedes shop manual on 2 CDs is of such poor quality and limited scope that following that wiring chart offers too little information.

And, the MAT - Omega owners' manuel offer limited insight.

Thanks in advance for any help!