I have an 1987 124 wagon. The only symptoms are the stock USA left leadlamp unit works wrong. Turn on parking lights, the left headlight and fog turn on. 3 of 4 wires from the harness are hot with switch in parking position. Turn on the left turn signals with, headlight off; the headlamp flashes. headlamp on; no left turn signal. Mice HAD eaten the insulation of some wires in the left front corner, but there were no signs of shorting when I replaced them. After studying the schematic (and not having a schematic of the module itself) I believe that the headlamp current flows through the module, rather than just getting signal from taps. Is that correct? With late 70's Honda Goldwings the modules always malfunctioned and a series of jumpers allowed operation with module removed, relying on the operator to check the lamps occasionally, like good drivers do anyway.
Have any of you bypassed the module, or do you just buy new parts and hope it wont happen again?