In trying to troubleshoot the many problems of the ACC in my wife's 83 300D, I noticed that the center flap always remains in the closed position. I checked the voltage to all the electomechanical switchover valves and all read 13 volts when actuated by the pushbutton control unit. #3, which controls the center flap, only reads 8 volts. I substituted another control unit from a parts car and got the same result- 8 volts. When I swap another lead from #2 for example, the valve opens. Why am I only getting 8 volts here? Where should I look for the problem?

Any help would be appreciated

Rick

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