Dear Forelle,
To be honest there should never be a time when you switch off the fans on the PXI chassis - or any fans on a desktop computer come to mention it.
The fans in the chassis provide two funtions. The primary function is to cool the components (cards, processor board etc.) inside the chassis. The fans also have a filter on them to clean the air entering into the chassis which again is there to help prolong the life of your chassis and interface cards.
Would you consider turning off the fan that cools your car engine simply because it is noisy? The same logic applies to your PXI system. Some of the boards such as the RT boards run hot (sometimes too hot to touch!) and this is when used inside a chassis with working fans.
While I appreciate tha
t the level of noise is often inconvenient, particularly if working inside an office environment, disabling the fans by simply removing the fuses is a sure-fire way to cooking your PXI system and an expensive repair bill!
Jeremy
