Sounds like another Duovalve failure.
MOST complaints of a Crossfire (and many Mercedes) blowing hot air with hte A/C on are not A/C failures, they are duovalve failure. The duovalve is the gate thru which hot water flows to the heater cores. Unenergized = full flow and hot air. SOmehow, they tend to stick OPEN not closed.


Watch the video: