I'd also recommend having it checked out with the dye first because the evaporator isn't the only part of the AC system that's prone fail on these cars, there's there's also the condensor that gets hit by road debris, the compressor and a hyper-expensive tube between the components and that's what failed in my car. I am told that the70 series evaporators don't fail as often as the 850 evaporators, but that word came from my Volvo dealer while I was complaining about my 70's AC so......

$850 seems a good price, considering that the evaporator replacement involves gutting the dash. http://www.volvospeed.com/Repair/ac.htm Look at the photo at the bottom of the page.

PLEASE let us know in the event that Volvo picks up the tab for the evaporator!!!!