'00 A/C troubles

'00 Windstar, 240k miles. A/C quit working this winter when defrost was on. So now that it's warming up, here's my troubleshooting info:
When controls are on any A/C enabling position, I have 12 volts at both the fuse socket and relay socket that are in the fuse panel under the hood. On the relay socket, that's 12 volts across both sets of terminals. With both good fuse and good relay, compressor doesn't come on.
If I jump across the high amp (the controlled) terminals, the compressor clutch engages, but the cooling fan doesn't come on.
Since the A/C won't come on by itself, I haven't been able to check whether I have a charge in the system.
What's next?

Don't know if this will help you but my truck did that I after a bunch of messing around I fond that it was low on Refrigerant. It would not let the clutch engage. Once I filled it, it would engage. Fixed my problem.

My 2000 did this also. Mine was low on refrigerant due to a leak in one of the ac lines going to the rear of the van. Unfortunately when the lines were mounted to the underside of the car a portion of the line was rubbing against the frame. Made a nice little hole! Refill with refrigerant that has the green dye. Look for leaks.

OK, it took a while to get back to this. No, it's not low on refrigerant. I jumped the compressor relay terminals so that the compressor would run, then checked the pressure. It's good. I read somewhere that the sensor on the side of the accumulator/dryer that goes bad. Is this true? This is a pressure sensor, right? Anybody know how to tell if this is bad? The local auto parts store doesn't have a clue what I'm talking about, and the nearest Ford dealer is 40 miles away. So I buy most of my parts through RockAuto.com, but they don't seem to list anything. Help!!!

Looking on Rockauto......the accumulator listed for your 2000 windstar (assuming 3.8L) looks much different than the one for my '96.

However......I DID find the A/C cycling switch....which they list as being the same switch for 1996 - 2003 windstar.
They do not list these pressure switches under Heat and A/C where I first looked.....
It is listed under "Electrical Switch And Relay"......then select "A/C System Switch"

The "Pressure Transducer" on Rockauto is listed for 1999-2003.
Then to complicate things.....they list some other pressure switches, with different part numbers under "A/C Clutch Switch".

Maybe you can make sense of the information and get the correct switch for your 2000 system.

This is a link to a picture that identifies the A/C cycling switch and the A/C High pressure Switch, ....
NOTE that your 2000 might be laid out differently.....particularly as your accumulator looks different.
http://rides.webshots.com/photo/2077761460011220610tpjsMq