Its not wireless. Check the socket on that side. My post from June 2006 follows. Many people have had this problem. Since 2006, there are probably new "fixes" and wiring harnesses available. It is fixable.
"I had this done under waranty on my 02 C230 coupe. As you have found out the bulbs and the old turn signal holder create arcing if they are loose (many cars have loose fitting sockets) which causes intermittent signal failure. New bulbs don't solve the problem. Both of mine failed.
I have looked at my car to assist you if possible.
On the drivers side the new socket has BROWN and WHITE wires. The BROWN goes directly to a painted screw near the suspension tower (other brown wires are already there). The WHITE wire goes into what I assume is a fuse or relay with "PBT GF15" on the side. A BLK/WHT wire emerges from the other side. The BLK/WHT wire disappears beneath the black cloth tape that covers the wiring harness with the following 4 wires in it. Four wires; BLACK/GREY, BLACK/YELLOW, BLACK/WHITE & BROWN all go into a connector mounted behind the headlight. Dealer made no attempt to remove any pins but instead soldered or wrapped tightly the wire underneath the black cloth tape. I do not want to remove the tape but I can tell you the whole job took less than a half hour at the dealership.
For the passenger side the BROWN wire goes directly to a painted screw to the left (outside) of the coolant system overflow. (other brown wires are already there). The WHITE still goes into the "PBT GF15" and on this side a GREEN/BLACK emerges. The GREEN/BLACK also disappears under the black cloth tape on the wiring harness that is connected to a connector mounted behind the headlights. The four wires on this side are:RED/GREY, YELLOW, WHITE & BROWN. None of the pins or connectors have been cut or removed."