This relay provides the delay function on your wiper motor. If your wipers are not working in the first postition on you switch it may mean this relay is bad. It is located behind your instrument cluster up close to the firewall on all 123 chassis. On 126 300SD and 380SE it is located inside the fuse box. Good used working relay. Even if yours is not bad you might want to pick this up for a spare when you need it!