The overdrive on my 1990 240 Wagon quit working and the dash light came on. I checked the gear shift wiring, per Mr. Bernstein's instructions, no joy. I replaced the relay, again no joy. I ordered a new solenoid via ebay and set about installing it. The solenoid was fairly easy to get to but the wiring connector to the gear shift wire was impossible to reach. I ended up cutting the existing wire and the new wire where both were accessible and spliced
them together with compression connectors. Before doing the connection I slipped some heat shrink tubing over the cable. After doing the connection I coated the connector with dielectric grease, slid the heat shrink over the connector then filled each end of the tubing with more grease. Using a heat gun I shrank the tubing. Thus a waterproof connection and a working overdrive.