Why Low Voltage at ACC Switchover Valve?
 

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

If the 123 is like the 126, the switchover valves have constant ground and switched power. The center flap switchover valve is an exception; it has constant power and switched ground.

Sixto
91 300SE
87 300SDL
83 300SD