Rambo box fan question

How often should the fan run on the Rambo electronics box of the TAZ 4? The fan on my printer never turns on. Do I have a bad fan or Rambo board, or is this normal?

I had what appeared to me to be a heat related failure the other day, and that is when I noticed the fan was not running. Further observation over the last couple days verified the fan NEVER runs.

Any help here would be greatly appreciated. Thanks.

It should be always on.