Used compressors are plentiful and relatively inexpensive (~$65 on eBay). Paul Grant or Abran can likely get one to you. Again though, if the system is opened to the atmosphere you'll need a new receiver-drier (~$15). I wouldn't install the receiver drier if you're taking it to a shop to have the system evacuated and recharged; I'd have the shop install the receiver-drier too.

 

I did a bit more trouble shooting. The low side pulls a vacuum. The high side has positive pressure. A little research leads me to a bad or sticking expansion valve.

I'm hoping that it does not involve removing the dash.

 

Does anyone have experience replacing the thermal expansion valve? It's such a cheap part... but I can't find any info on removal except from the rave manual.

 

Have not personally replaced one on a Discovery, but it will be a PITA. What were your high and low pressures?