I've noticed that when my dehumidifier starts to blow hotter air than expected, the intake fan (usually on the back) is clogged with dust. Most newer units have a filter that can be cleaned or even replaced if need be. And if that doesn't seem to work totally, allow the dehumidifier to cool down by turning it off for about 1/2 hour or so. That seems to work great for me. My humidifier runs non-stop in my basement from spring until winter and I have to clean my filter about once a month. Hope this helps you out!
Dave, January 2008