The thermostat switch for the fan is located close to the tubing that exits the boiler tube. The tubing will continue to stay hot and will eventually cool down and the thermostat will turn off the fan. Turning the Use/Store to Store will turn off the power to the fan. Another thing you could do is put a switch on the power line to the fan. You might find the fridge in works well enough without a fan until the hot weather arrives.
I had a fridge fan in my Casita trailer which had a 4cu/ft fridge and I never used the fan as I didn't see any performance increase even in the hottest weather.
Just remember these absorption fridges are not that efficient and you need to get in and out of the fridge fast because they don't recover like compression driven fridges. I usually carry a cooler to keep drinks in warmer weather months. When its summer I keep the fridge on the highest setting. In Spring/Fall I turn it down to 4 or 3 to maintain the 37-40F.
2008 Classic 25fb "Silver Mistress"
2015 Ram 2500 6.7L Cummins. Crew Cab, 4x4, Silver
2010 Tundra 5.7L, Double Cab, 2wd, White