Update... I replaced the convenience relay with one from a later model. Original part number of 124-820-32-26 has been superceded by part number 202-820-09-26 in the Mercedes-Benz parts system for this application. This is appearantly the same module found in "C" Class vehicles (W202) and later W124s. Auto down works fine 100% of the time now on both windows. This feature is controlled 100% by the module.