the aircon compressor tends to cut out even when the temp is not cold enough. could it be the relay at fault? where is the relay, and how does it determine when to come on/off? any other suggestions as to where i should begin looking? thanks!

The 123's have a mechanical evaporator temperatur control that is set to cycle the compressor off at about 48 degrees evaporator temperature. This is not very cool to most of us since most other cars use about 38 degrees for this cutout. Additionally there is a cacuum controlled solenoid that closes a door limiting outside air into the system. If this is bad then the system continues to try to cool down outside air versus recirculated air. Both of these can be modified or repaired for better performance, especially if you are in someplace like Texas, NM, AZ, OK, etc where the heat is oppressive.

Compressor control is different for the different models. What year and what A/C? Late 240Ds have an electronic control within the temp wheel which reads a variable resistor.

All the other 123 A/Cs use a ETR switch (evaporator temp regulating) which has a capillary tube into the evap.

the car is a w123 200 M115 engine.
How do I get to the ETR switch (evaporator temp regulating)? Where is it?

where i'm from, the heat IS oppressive ...

thanks!

Roland,

We still must identify your A/C system. Being in a entry level model I presume you have manual controls and not Climate control. If the car was made later than about 1981 then it won't have a ETR switch it will have an electronic control in the temp wheel - Do you have a temp wheel or a rotating knob?

If you have a ETR switch it is easily exposed by removing the lower panel passenger side and its roght on the face of the evap housing, covered with insulation.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

hi steve, i definitely do not have climate control and it's a temp knob that i have. so what should i look for now? thanks again!