Everything on these newer cars goes through a relay.

Just because you turn a switch, no longer means you have directed power to the desired motor..... The relay "decides" if you are going to get what you request.

Time to pull the codes with the MB diagnostics.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles