AC blows cold air when car is not moving, then hot air when moving.
You haven't said what model and year but this is fairly universal.
1. Check the coolant level. If you have a sight glass, are there
bubbles when you rev the engine? If so, there's low coolant.
2. No bubbles, then there's a vacuum leak and the car goes to the warm
side when the vacuum increases.
I think #1 is the best guess.
Go to a good AC guy and have the pressures tested. I *think* you'll
find the coolant (once called Freon) is low. Slow leaks are common and
they reveal themselves every year or two.
Also, get a thermometer for the vent (couple of bucks). You should
easily get 40 F at the vent when everything is working properly.
I used to do my own AC and readily got nearly 30 F at the vent with a
new drier, good vacuum, and coolant charge. Even with the new stuff
(134A?), I easily get under 40 F at the vent on a hot day.
Chuck Fiedler
Nothing but Volvo since 1974
