The Middle Atlantic Products proportional thermostatic fan controller extends equipment life and reduces service calls by varying the fan speed of up to four fans based upon temperature. The fan controller has 3 temperature ranges and can be set to operate the fan speed either proportional to temperature, or to come on full speed when the temperature threshold has been reached. This UL Listed device can also be turned on or off via a local switch, and includes status LEDs. The fan controller can be mounted to rackrail brackets or any flat surface, and is also available as an MPR series module and is manufactured from galvanized steel with a durable min-spangle finish.