1999 Mitsubishi Montero AC stops working after runing for a

Hi Mauro Madrigal. Welcome to the forum. Dandy observation about the clutch. Sounds like it is slipping from the increased load as the high side pressure builds up. If you can tell if the pulley is remaining up to speed, that will eliminate belt slippage. Before condemning the clutch, measure the voltage across the two wires in the electrical connector. If it is significantly less than battery voltage, the next step is to determine which circuit, the feed or ground, has high resistance causing a voltage drop.

Pitted contacts in the compressor clutch relay will cause a voltage drop that could increase as they heat up. A quick test is to switch the relay with a different similar one.

Caradiodoc