Mercedes C-Class - Compressor does not switch on | HELLA

Mercedes

C-Class (203)

With automatic-air conditioning

Compressor does not switch on

Radiator fans running at full power

If the air conditioning compressor in the vehicles mentioned above does not switch on and/or the radiator fans are running at full power, this may be due to a faulty SAM module.

If no error code has been stored in the ECU error memory, the error memory of the front SAM module should be read. The SAM module is an "intelligent fuse box" that is built into the engine compartment (see figure for example). If this contains a stored error code such as "Refrigerant pressure/temperature sensor- short circuit/interruption," the fuses, sensor and associated controller should be checked. If there is no signal at the sensor when the air-conditioning system is on, this may be due to a defect in the SAM module. Before the module is replaced, the compressor should also be checked for damage and to ensure that it is fully functional. This can be done using the "CLT1" tester, for example. This can be used to control the compressor (control valve) directly.

More information on checking clutchless compressors can be found in Hella Tech World (Technical info: "Clutchless compressors" + Know How Tool: Video gallery).