Since it has been mentioned, yes the expansion valve was replaced about 2-3 years ago.  After it was replaced it did not fix anything.

I do not know what the gauges read, if I did I would let you know.  We are not A/C experts so we have always hired someone for charing it.  It has been checked several times at both idle and full throttle and nothing seemed out of the ordinary.

The viscous fan drive has been replaced three times in the last two years (cheap crappy clutches) so there is no way that is part of the problem.

Is it possible that the heat of the engine once you start working is gathering under the hood and making the A/C unit hotter than usual?  Because when you turn on the A/C when you are working it only makes the air less hot, not cool.