I thought I'd run my air con, since they recommend doing it once a month. It was regassed last summer, so that part shouldn't be a problem. So I put it on with the blowers on full, and warm air came out. I experimented, by turning the heater setting up to highest, but with air con on, and the heat came out even hotter. Then, I turned the heater back down again, and finally the air started to come out cold. The act of turning the heater way up, then back down again, seemed to allow the cold air to come out. Why would this be?