What I've decided to do is disconnect the case fan from the PCB (3-4 pin connector) and install my own programmable thermostat that will power the fan and turn it on and off from user low and high temperature setpoints.
There's plenty of these programable thermostats on the internet with LED redout of the the current temperature and setpoint temperature.
Each thermostat controller has a water proof temperature sensor that can be installed in dry or wet locations.
You can program them for either cooling or heating with a min and max temperature setpoints.
With some experimentation I would need figure out the best min and max. temperature setpoints.
For cooling I would program the thermostat to come on at I don't know 80 deg F? and then to turn off at a lower temperature.
I'm looking at one with dual led display that displays the current temperature and also a setpoint temperature, such as the temperature when the fan will turn on.
Some come with a case where you can install on the outside of equipment or others a face plate to install inside of equipment case, etc. They're not very large in size and don't take up much room.
Some only display Celsius while other can be configured to display either Celsius or Fahrenheit
Most can handle devices such as fan, heaters, lighting, etc. up to 10 amps while other up to 20 amps. Which should be enough for the Truecharge2 case fan. I'll need to take a closer look at the case fan to see what it's power, current, cfm ratings are. The size and how it's connected to the pub it's most likely a 12 volt fan.
The controllers below should be able to handle either DC or AC, some controllers are 12Vdc, 24Vdc, 110 Vac and 220 Vac. You should be able to connect a 12 volt power source to the thermostat and have the thermostat supply power to a 12 vdc fan up 10 or 20 amps.