Took my Vanagon back to see where the dye leaking out. Mechanic says 'compressor front seal'. He recommends replacing compressor and dryer. Quoted $500 for compressor plus labor, $85 for dryer plus labor plus replacing lost freon. Around $850 total he said. Also said expansion valve could be leaking but he cannot tell without removing roof molding (quoted $350 labor). This is all on top of the $1200 I paid to get the van thru emissions and fix a few other things.
To compare prices, I looked on Bus Depot website for an a/c compressor and could not find one. Though mechanic said he would not fit anyone elses compressor due to 'warranty problems'.
A/C actually works ok now with a full charge of freon but when it hits 110 degrees and after being parked in the AZ sun, it gives up. Eventually though the freon will all leak away.

-David ('87 Wolfsburg)