Switches are designed to be installed in the drain ports of the DC Series coolers, and in the reservoirs or piping of AC/ACD Series coolers.. Series Accessories: Temp Control Switch set @140 F Depending on how the cooler is plumbed, it can be used to control the temperature of the oil either entering, or leaving the cooler. Use these temperature switches to control oil temperature by cycling the cooling fan to maintain the desired entering, or leaving temperature.