evaporators are fine,and work very well, even with a compressor that has rings and valves that are in not so good shape. ya just gotta be smart enough to occaisionally drain your tanks.
dryers are fine, and work great when they are new, but, if any oil gets past the compressor, it coats the dessicant, so it work work properly. the first clue to that is when the spitter valve pops out oily water. another advantage to the evaporator is, there is no "spitter valve" to freeze open in very harse winters, which cause all the air to be drained out of the tanks, so the truck can't move, since the brakes are locked. every road service truck in the world has the brass fitting necessary to go around the dryer and make it useless, so the air can build up.
the evaporator will work fine, as long as you remember to add some alcohol / methanol in harse weather, and remember to occaisionally drain the air tanks. in fairness, the dryer is pretty much the preferred system, and works very well, until it fails. i guess i will leave it at that, since you just asked what the evaporator does.
