Last summer my 850 was diagnosed with the dreaded evaporator leak that the dealer would fix for $1500 (they used the fluorescent dye recharge kit). It doesn't get hot enough in SD to warrant that kind of money. So I added 1.5 cans of r134 last summer and it lasted about a week or two. This summer I used a sealer by Interdynamics (got it at Pep Boys for about $12) and recharged with r134 again. I figured that what could it hurt to try a sealer and see how long it lasts - I'm a scientist so I've got to experiment. I did this in early May and it's just now starting to peeter out. So maybe I've partially fixed the leak. All that I can tell you is that the recharge lasted longer this summer with the sealer than it did last summer without. I'm debating trying it again this summer or next. Probably depends on how many hot weather drives I have left in the summer.

JMO - good luck!