Agricultural systems fail for mechanical reasons far more often than automotive ones. The refrigerant circuit is the same; the environment is not.
Airflow is everything
A condenser packed with chaff loses most of its capacity within a day of combining. Blow it out from the fan side every morning during harvest, and fit a mesh pre-screen if the machine does not have one.
Hoses and vibration
Long hose runs on a tractor move constantly. Check that clamps are present and tight, and that hoses are not resting against a chassis edge. Most agricultural leaks we see are chafe points, not fittings.
Cab pressurisation
A cab that no longer holds positive pressure lets dust in and makes the operator open a window, which defeats the system entirely. Replace the recirculation and fresh air filters, and check the door and window seals before condemning the cooling.
Spare parts to carry
In season, a spare drier, a compressor belt and a set of O-rings on the shelf will save a day's work. Compressors and condensers for common Claas, John Deere, Fendt and New Holland machines are held in stock for next day delivery.