Originally Posted by Mark DiSilvestro
Unfortunately, the component labels on your diagram are nearly illegible on my display and I'm 200 miles away from my FSM this week. so I'm going by memory of how my '72 W114-115 AC worked.
Does your change-over switch activate the heater-fan in the dash, then the AC blower in the console as needed? Do you have power to the AC compressor thermostat? In the OP's photo it's one of the two green wires connected to the square metal device in the console, controlled by the rotary AC knob. When the thermostat is getting power and it's connecting to the compressor, you should have 12V at both wires.
Happy Motoring, Mark
I spent some time and I compiled some schematics and drawings of the A/C system. I opened up the center console and tested out the wires on the back of the A/C rheostat/C O L D E R knob. Some of the terminology on the Mercedes schematic is confusing, but I think I've got it.
I'm looking for input on if anybody thinks I have a bad A/C rheostat /vacuum control/ C O L D E R switch?
The drawing is of the female end of the change-over switch. The Mercedes wiring diagram draws the circuit in an out of order orientation to the switch. So this is helping me out. I have 12 volts at location 4. Nothing else is energized.
The vacuum system appears to be working properly.
I do not have 12 V at the A/C rheostat knob. I tried to energize the switch with 12 volts and nothing happened. I may have a bad switch, or bad wiring. I am pretty sure the 6-pin change-over switch can only be inserted one direction. I tried to flip it around and the plug really didn't fit.
As you can see in the pic I have a floating wire from the A/C control light. I am not sure where that goes. Any help there?
Hopefully we can get this figured out.