Mercedes-Benz W164 A/C compressor and fault codes

Start with the high- and low-side pressures of the refrigerant circuit, which must be within the reference values. Then check that the auxiliary fan at the front works, as its failure is a common cause. If the diagnostic tool shows no fault and the evaporator doesn't cool, there may be too little refrigerant or the compressor may be weak.

Code 9006 indicates a short circuit in the refrigerant compressor. Replacing the compressor alone may not fix the fault, so use the values from the Star diagnostic tool to locate the actual cause before replacing the part.

The pulley bearing turns whenever the engine runs and can seize. The pulley hub has a thinned section that gives way when the compressor seizes, protecting the belt drive. A rubber coupling connects the pulley to the compressor shaft.