Check your wiring diagram for the 1992-95 S4/S6 vehicles for any changes. The resistance from E2 to E3 is only ~0.2 ohms and the 2nd speed fan current flows through this resistance and drops some voltage for correct 2nd speed operation, the resistance from E1 to E2 is also ~0.2 ohms.

The resistance from E1 to E3 is ~0.4 to 0.5 ohms and this measurement goes through two resistance's (E1 to E2, then E2 to E3) which are used to drop more voltage for the 1st speed (low) radiator fan. If the resistance element from E2 to E3 burns up, you will lose the 1st and 2nd speed operation, if the resistance from E1 to E2 burns up, only the 1st speed (low) will stop functioning.