Mercedes-Benz W210 A/C compressor does not engage
Why does the W210 A/C compressor not engage?
The most common cause is low refrigerant. The pressure switch prevents the compressor from running if there is not enough pressure. When the compressor engages normally, the magnetic clutch clicks and the pulley starts to turn; cycling on and off is normal.
What should I do if the refrigerant has leaked out completely?
The leak must be found before refilling, for example with a leak detector or dye. In a nearly empty system a vacuum test does not find the leak, so the system is pressurised with nitrogen. Leak points include the condenser and the dryer. Refilling and leak finding are a job for a workshop.
What if there is refrigerant but the compressor still does not engage?
The cause is then often electrical: the wire or connector of the magnetic clutch is broken or the clutch coil is open. The fault codes can be read with a diagnostic tool, and they should be read and cleared after refilling, because the automatic climate control may otherwise not start. A faulty pressure sensor can also interrupt operation.