Turn off the power and unplug it.
remove the cover on the back - torx fittings about a dozen.
At the top you will see a couple of black electrical connectors - one has a small red button.
Press the red button - if it clicks then you have fixed it. This is the overheat protection.
Make sure that the filter and the internal filter are clear - this is the most likely cause ov overheating.
mark
January 2009