نشتی کاسه‌نمد شفت کمپرسور

The seal around the air conditioning compressor's input shaft, leaking refrigerant and oil. It is the one dynamic seal in an otherwise static system — the shaft turns whenever the clutch is engaged — so it is a wear point rather than a defect.

The evidence is oily residue around the compressor's nose and clutch, which collects dust and is visible without any equipment. Long periods of disuse make it worse, since the seal dries out when the compressor never turns — which is the argument for running air conditioning briefly through the winter. Where the seal has failed the compressor is usually replaced as a unit, and the system needs evacuating and recharging by weight afterwards rather than topping up.