1993 400SEL Doorlock Problem. Power doorlocks not working, either by fob or key, signal is being received. Works for a day or so after all settings are reset, but then quits. I have replaced the chasis brain box twice with used parts(#1408200026-0001), but same thing keeps happening with one exception. With the original box, when the the door locks stopped working so did the express window feature(automatic up and down). With the two replacement units the express feature continues to work regardless of the locks.

Other quirks; With the newest unit in place, the automatic closing of windows and sunroof with fob did not work and when trying to lock doors with dash control, the overhead lights flashed for a second(I have replaced tis unit also).

Any suggestions would be appreciated!

Richard