Advanced dock 2503-10U: fan suppose to be on all the time?

[Wesley]

Hello,

I recently bought a used advanced dock and I was wondering if the fan is suppose to be on all the time or does it kick into action when it's needed? It's for my T61. I have an IBM stamped docking station and a Lenovo stamped docking station. The Lenovo station's fan doesn't turn on, whereas the IBM's fan is always on.

Just a side note, the pcie fan is much more quiet on the Lenovo station than the IBM station.

Thanks