Dude,

If you do a search, you will find that the 850 has A/C problems that extend beyond the boundaries of space and time.

The odds are that you do indeed have a leak(s) in the evaporator. This, according to my experience (with my own 850 as well) seems to be the most common problem.

As far as a leaking A/C system goes, you really have about 3 options:

1) replace the evaporator. This is the most costly and time-consuming solution. In order to do this the ENTIRE dashboard must be removed. Not really a DIY job. If you do this, expect to pay at least $1200, possibly as much as $1600 to $2000 for a professional job. While you've got the dash out, might as well replace every bulb in the dash.

2) Inject some kind of "stop leak" into the system. Some mechanics will tell you that they have a superior chemical that can be injected into the system, and will probably charge you over $200 for the job, but ignore them. I will tell you from experience that Quest "Stop-Leak" (i think it's called that) which is sold at AutoZone for about $19 will do the job superbly. Before I used it, I had to completely recharge my A/C EVERY 3 WEEKS! After using it, my system stayed fully charged for the entire summer, and evem through winter and into this summer as well. Great stuff.

3) Sell your car. Of course, I know you don't want to give up your Volvo, quirky though it may be.

If you use the stop-leak, make sure you have refrigerant on hand because you need to fully charge the system after injecting the stop-leak, then let the A/C run about 15 minutes.

I don't know if this answered any questions, but if you have any more, just ask.

kevin