2004 Subaru Legacy AC quits working after 2hrs

Sure, Midnight4,

This sounds as though your air conditioning has maxed out and there is a potentially frozen condensor.

When the condensor is iced up, air cannot blow across it and therefore your air conditiong will not cool the interior of your car.

I would assume that after you stop for a while and shut the engine off, within about 15 minutes the ice will melt and you can use your air conditioning again.

The recommendation is to report the problem along with this analysis to a qualified repair professional.

The air conditioning, thermostat, electronic sensors, and other controls all need to be investigated in order to conduct a proper diagnostic procedure and resolve this problem once and for all.