Orrrr Pete, the pressure switch is failing causing the system to cycle on and off like its doing. Thats another theory. But if its crazy cold, it could be charged correctly. Oh another thought that just occurred to me, our systems have a thermistor that cycles the compressor off to prevent the evap from freezing which is actually more of your issue now that I think about it. So if the thermistor triggers the entire AC system to switch off, why keep the fan running when the compressor isnt pumping any freon through the system.
I dont have an Efan on the 2.5L to help figure this one out but thats just my idea on how its all operating.
This being said, does the efan stay on the entire time until the thermistor reaches the temp to cycle the compressor on and off to prevent freezing?