ok, I remember something that did not work for me but may work for You...supossely the evaporator temperature sensor should not read more than the heater core temperature, this would cause strees to the n22 (climate control unit) and not knowing what to do, it would shut the compressor off....

read....

http://www.asashop.org/autoinc/jan2006/techtips.htm

have You changed your evaportaor sensor lately?...it is around 40 dollars, and it is worth the try...