Try popping the conectors off the bulbs in the lamps. Only those are on when side markers turn off correct? If that doesn't work, 600 bucks for a new switch is better then 100+ bucks batts once a month. Mopar is related to this electrical switch faults. Check the late 90's rams and durangos switch. Is it related? Around the same time chrsyler got bought out by the ****'s. I've had em. its cheaper then a new harness trust me. Or you can redneck ur slk and disconnect them completely. My personally, i put a complete light bar on the roof so i can hit them deer at 148. FIX IT!!