Most compressors have a thermal overload switch that will automatically shut the unit off when it gets too hot. Once the compressor has cooled down, the switch will reset and the unit can be restarted. The length of time it takes for a compressor to cool down depends on the size and type of compressor, as well as the ambient temperature. A small air compressor in a cool room may only take a few minutes to cool down, while a large industrial compressor in a hot warehouse could take an hour or more.