Hi Ed - for that fan to work, the refrigerator has to be running and the temperature in the condenser coils next to the fan has to be above a certain level (I seem to remember 120 degrees F, but I could be wrong). If those conditions are met, the fan SHOULD run with the top down, in fact it is important that it DOES run then so the condenser can be cooled properly when you are stopped while traveling and the fridge is on.
So, if it is NOT running then, I would guess there is a wiring problem. AND, I don't really have any great suggestions for trouble shooting. It is NOT controlled by the Master Switch, only by the switch near the fridge and the fridge operation/condition.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew