Not having the fan on during the smog check would do little in the way of
causing your BMW's radiator to start leaking or develop any type of problem.
When ambient air temperature is above 70f the BAR requires the fan to be
placed in front of your vehicle to help engine cooling, however even without
it your car's cooling fan should provide enough cooling as to not cause
overheating. The smog station's fan is simply there to assist. Not using the
smog station's fan will not damage the engine, but on a borderline passing
vehicle, not having the station's fan on could cause it to produce high NO.
posted by SmogTips Support