Just a thought: running the fans all the time just wastes wattage over perhaps 40 mph - they can't deliver air as fast as the grill does.
What to do?
I can't think of anything for you (auto trans) but a stick trans can have a switch that interrupts fan power in high gear (breaks the low power signal from the switch to the relay). This way it's always off when you don't need it, and no worries about remembering.
