I used to service my own AC when R-12 was 99cents a can but now it is expensive and there are environmental issues. I can't afford to take the risk. I found an AC shop that will suck all of your freon out and let you drive it home and replace any parts necessary. They will also do a discharge and recharge if you don't need A/C work but have to remove your compressor to fix other stuff on your car.
When you bring it back they charge you a flat rate for recharge plus the additional freon you need over what they sucked out. They are honest about that too. It saves me enough money to justify replacing everything that might reed replacing so I don't cut corners which would cause the job to go bad on me later. It also assures me that the system is recharged properly and leak tested.
They have all of the business they can handle and the recharge is the quickest, cleanest and most profitable job they do so it works out well for everyone. They get parts wholesale and sell them to me at retail (which I would pay for them anyway) so they make a parts profit on the deal too.
I would suggest dropping in on a few A/C shops in your area to see if you can find a similar deal.

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL