It is nearly impossible to use the fan without the light.  If we have both lights and fan on, all works. If I turn off the light, while leaving the fan running, everything turns off.  It then beeps or clicks two to three times and the whole unit just turns back on, light and all.  The fan then shuts off.  So basically you can use the light, you can use the light and the fan together, but you can't use the fan by itself without the whole unit shutting off, then turning the lights back on without the fan.