I agree about drying it out, conceptually, but not sure about 400 degrees? .Some have plastic stuff in there, as well as a max temp for the drying media. Or if with glass window might crack it? differential expansion, melt solder? Etc
It will work , apparently to the user, if 100% non functional as a dryer, too!! if no water in system, no dryer, AC works. another aspect..
I think but am not sure that the early ones have that stuff that turns pink and blue in there..sometimes present in a sight glass too. Once you are over 212 all the water will turn to vapor . might flush residual vapor with squirt of refrigerant of dry nitrogen a few times too .
Maybe someone has those recyclable shop air dryers which come with instructions for drying it out. What temp? I doubt is needs 400, might cause a new issue…? Similarly acetone might dissolve the good stuff. Or worse, put stuff in a form that breaks off or is loose granules. Tread lightly?.
I will chime in here. If you can blow throw an old drier it should have remaining life. I opened a 55 A/C system that was not functioning. I flushed the dryer with acetone that will clean and displace moisture, drained it then blew it out with compressed (dry) air. If you do not immediately install, plug the fittings to prevent moister from entering internal dryer media.
I was able to get 40 degree air at the outlet register.
You can probably buy a new one pretty cheap, but if you look at old car restoration the same way I do, you would rather restore an old part if you can than go out and buy a cheap new one. I've often spent an irrational number of hours restoring some part of an old car rather than just picking up a Chinese replacement. I remember well how it totally raised my blood pressure when my body shop lost a bunch of the factory original screws for my 300C. Sure, the hardware store might have pretty similar new ones, but that just ain't the same in my book. The receiver/dryer is in the same category. You can save it, so why replace it?
Here is what I posted a week or two ago:
------ If you can't or don't want to buy a new receiver/drier (which is your A/C system's garbage can) it is possible to "rejuvenate" your old one. Use an old toaster oven - which you probably keep around anyway to bake paint on small parts. Take it out into the garage or outdoors and bake the receiver/drier in it at 400 degrees for a couple of hours. It may stink to the high heavens, but that process will boil out whatever garbage is in there - same as turning on your self-cleaning oven. Give it a new coat of paint, bake it again at 250 for 15 minutes, and it will look and perform like a brand new champ again.
It's easy. Enjoy.