W461 lights suddenly non-operational

Looking for help! Last week I woke up to find my batteries drained. A mechanic came out and charged them up but now I discover that my lights don't work, headlights or turn signals, yet all the fuses check fine. I have disconected the batteries for now, wondering if here is a connection between the lighting fault and the battery drain. I asked for help on a facebook G-owners group and some talked of the stealth driving mode which switches off all lights, but despite having the original military-style switch I have never been able to access positions S1, S2, or S3.  I have removed the switch and there is no sign of burning or damage, and all connections appear good, it was replaced about a year ago. Any ideas?