Go to the hardware store.
Ask for a MECHANICAL DIAL TYPE wall thermostat for a HOME AIR CONDITONER
This is a high amperage thermostat for AIR CONDITIONING. It has four wires sticking out of it.
The four wires are TWO PAIRS, meaning in 300 years when one side wears out, connect the other pair. There are clear diagrams.
Screw the thermostat to the inside ROOF of the compartment. Spin the dial on the thermostat until which temperature you want the fans to come on at. The dial has painted numbers in Fahrenheit on it. Hard to go wrong. Adjust to your taste in temperature.
From then on, it's all automatic. When it gets hot the fans come on.
Slam the compartment door and forget about switches. The thermostat dial when turned all the way down clicks the whole shebang off just like a switch.
The wiring of this thing is so simple it is hard to believe. Just connect with butt connectors.
Rated for 25 amps DC. It'll do the job and there ain't no steenking batteries.
Turn off the electrical system (batteries) for the winter or when storing for long periods of time.