79 series airconditioner

Over gassed or no airflow through the condenser.


Licenced A/C technician

Could be many reasons but first thing to do is identify if it is a refrigeration or electrical fault, to do this safely you will need to know the pressures and to use anything that will give you pressures other than onboard diagnostics if equipped you should be lisensed.

Edit
If you are located in Australia.

Thanks Ivan and QC,

Checked the gas, cleaned the internal fan vent. The TX valve maybe freezing up, but, being on the coast cannot get the outside temperature to above 30 degrees, to replicate western environment. The Denso unit we have the clutch cannot be replaced, it is all or nothing. Going to bite the bullet and buy new unit and TX valve. $$$$$$$$$$ RN

How is your coolant temperature on those days does it run hot ?

As others have written there will most likely be high and low gas pressure switches. If either is faulty or the gas is low then the compressor would switch off pretty quickly.

The 78 series which I assume would be similar to yours also has a lock sensor in the clutch assembly, a faulty lock sensor circuit will also turn off the compressor quickly.

A faulty AC realy can also cause all sorts of issues.

The other issue is under temperatures can affect connections, switches realys etc, you could try heat the the pressure switches, AC relay etc with a temperature controlled hot air gun and see if you can provoke the fault that way. Simply deciding one part is faulty without doing any real diagnostics is most likely going to be an expensive way of finding the fault. If you don't have the electrical skills to diagnose the problem then take the vehicle to someone who has.