Symptom - Van AC works just great until the things warm up.
Observations - Seems to work just fine till my first red light. When stopping, starts to blow warm air. Also, observed that the radiator electric fan completely stops, yet the AC compressor still appears to be engaged the entire time.

HOT days like today, when I want it most, is when it works the worst. Cooler days, it seems to work just fine.

Suspected a fan issue, and when I by-pass a relay and force the radiator fans to stay on, the problem seems to be much better---yet still not perfect---I still get SOME drop outs at stops.

Theory now is that the clutch is slipping. Revving the motor seems to bring it back to life. The reason that forcing the fan on seems to help is that causes head pressure to be lower then it normally would be. (considering the engine compartment environment is really really HOT). Running the fast fan lowers that temp a lot. The lower temp means lower pressure and that is less work to turn the compressor, and thus it turns more often, and works for more of the trip.

I cant just leave the fan relay bypassed cuz the fan would run 24/7 and thus run the battery down. I am thinking that a cheep fix might be to rig up my own relay that engages only when the compressor engages. That I could do pretty easy right in the fuse box. Just cut the actual fast-fan trigger relay trip line, and tie it in parallel with the compressor trip line. That might be sly enough to actually not trip a service engine error code!

Its not ideal, the side effects would be longer warm up times, but don't really care about that in the summer...and I'd probably take a ding in AC efficiency, as the there will be some times, again rare in the summer, that the compressor should be on with zero radiator fan running.

Any thoughts?

When was the last time you had checked the R134 in your A/C system? Or put any in at all? As I mentioned earlier, sitting at idle, your refrigerant is not moving around very much in the system and with the car sitting still, no airflow across the condensor.

Here'* something to try. Get your garden hose and spray in front of your radiator.(to clean it out.) Test your a/c again. If not much change, dump a can of freon in.

Ya pretty sure that part is good. I had a friend put gages on it, and he said it looked ok. And when it is working, it works great.