Help with 300E W124 A/C compressor not operating

[vtechnician]

Refilled the air-con gas.
Jumped the A/C compressor to battery +ve and the clutch works.
Jumped the pressure switch for the refrigerant compressor-still doesn't engage the clutch.
Tested the compressor cutoff relay and the wiring - all is good.
Replaced the control unit,automatic temperature control which is behind the glove box.
Removed the operating unit,automatic temperature control which has the temperature selector wheels,EC button etc.Stripped the unit and tested all the components.All seems ok.

Any ideas as to what the fault could be?

 

[WOODYTHEWISE]

How about the temp sensor for the evaporator? Double Dutch to me,however,the fault I had was like yours,the main dealer replaced the sensor and all was OK/

 

[BoyracerAU]

I've heard two common causes of failure are the OVP and the speed sensor on the back of the compressor.

 

[vtechnician]

Problem solved.
It was the 3-pin temperature sensor.Unplugged the single connector and the A/C compressor now engages.
Thanks for all the help.

 

[martin anderson]

got a similar issue on my CLK, a/c technician says the clutch on compressor won't engage. i'd like to try unplugging the temp sensor-where is it located please.

 

[jaymanek]

Relays are also dicky on these... I just replace them as a matter of course at this age.