Is there anyway I can recover the R-12 using only a manifold guage and canister? Is a vaccum pump absolutely necessary. also my can't CANNOT be moved. thanks.

 

You need a pump. Are you converting to the new 'environmentally friendly' crap? If so, then you have to get all of the R12 out; otherwise the system won't work properly. Also, when you suck it all out, it creates lower pressure inside your AC system so when you fill it with the new stuff, it will get sucked back in. It will allow to squeeze more into the system while maintaining the proper hi and low side pressures. It is also recommended that you replace the receiver/dryer. It's basically a large desicant pack that removes moisture from the system. Be sure to have the system checked for leaks because if it's leaking, then you're wasting your time.