I would more strongly suspect the compressor, although an expansion valve is certainly a possibility. It will cost you a new dryer if you're wrong, and that's not so bad.
Draining the oil from the compressor will probably tell you the most. If it comes out with a lot of debris, you probably do have a bad compressor.
I would recommend replacing the condenser rather than attempting to flush it. The fine passages make it difficult to properly purge all of the flush solvent from the unit.
Linear Mode
