Is it possible to pull enough vacuum on a "closed" A/C systems receiver dryer to dry the desiccant out enough for reuse? This should be feasible - has anyone calculated or attempted this? Also, can the receiver dryer be removed (cartridge type) and heated in an oven to dry it out?
I am using an "extra strength" Vacuum Pump (a Varian 2 stage used to rough Turbo & Cryo pumps) to evacuate the A/C system on my 1989 Toyota pickup truck (340kmiles). I had the evaporator out for a few days while leak testing it, and covered the suction/liquid lines at the firewall with tinfoil (should've done better job capping it). Finally found a failed O-ring, replaced it and other O-rings, re-assembled system, and pulled an 8-hour vacuum. Back filled with Nitrogen (dry, high purity), and after 8 hours have lost 4 pounds of pressure. Plan on pulling another 8-hour vacuum, re-charging with R-12, and hoping that the UV dye I have added will find the "undetectable" leak. Possibly the R-12 molecule will be too big to leak as the Nitrogen has slowly done. Can I do a few more "fill/pump" cycles with the Nitrogen to dry out the receiver?
Any useful information is greatly appreciated. Thanks!