What happens if you dial the Set Point down to, say, 64°F? And do you have some method of preventing temperature stratification? I keep a small 12vdc 120mm PC fan running in each of my ferm fridges when I have beer brewing.
Anyway, can't find a manual, but found enough info on the single-stage cool-only FE600 to perhaps obviate the need for one. The key item mentioned below is the fixed differential of 4°F. With your 70°F setting the chamber shouldn't get much warmer than 74°F if the unit is functioning to spec.
"The Analog Temperature Controller used to control the temperature of a refrigerator, freezer, or air conditioner. It enables you to ferment and store beer at correct temperatures when the ambient room temperature is too warm. Your electrical cooling device plugs into this unit which plugs into the outlet. A remote sensor connected by a small capillary tube monitors temperatures. If the temperature rises above your set point, the cooling device is turned on. The unit features a 4 degree swing to help extend the life of the cooling unit's compressor. For example, if you had it set at 68 degrees, it would turn on at 68 degrees and go to 64 degrees before turning off. The unit has the potential to regulate temperature from 20 to 80 degrees Fahrenheit. The sensor tube can be inserted into a refrigerator or freezer, and still allows the door gasket to seal tight. Temperature range of 20° to 80°F. This Johnson unit can handle 15 amps or 1725 watts at 115 volts AC."
Cheers!