I have an 88 240DL wagon, and experienced intermittent problems with the overdrive relay/switch. I traced wires, adjusted the kickdown cable, replaced vacuum hoses, you name it, but the problem kept coming back. I finally pulled the relay out and removed the plastic housing from the relay. Inside is a small circuit board with a simplistic magnetic coil relay. Apparently over time, the spring which puts tension on the relay had lost it's spring. By bending the anchor tab - be careful if you try this or you could crack the board - you can increase the tension on the spring and fix the problem. It has been two days and there is no sign of the orange arrow pointing up on my dashboard anymore. This is a much less expensive fix than replacing the relay, even if you get one used or at a junk yard. If this helps anyone, let me know, it may work on other relays as well. Next time I may go to Radio Shack and buy a bunch of small springs to replace the old ones.