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


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).

Important safety note Technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only. Reprinting, distribution, reproduction, exploitation in any form or disclosure of the contents of this document, even in part, is prohibited without our express, written approval and indication of the source. The schematic illustrations, pictures and descriptions serve only for the purposes of explanation and representation of the instructions and cannot be used as a basis for installation or assembly work. All rights reserved.