I let my car idle for a while. The temp was at about lil over half way andI looked and 1 fan was running. Only the left one. The right one wasnt running. Does the other fan come on when it gets hotter or is it broke?

 

The other fan should be for the a/c.

 

Hi blue450yo,
You should be telling what car you have a problem with. But anyways, to disperse your doubts I suggest swapping the conectors on the fans (if possible) to check if the other fan is ok.
In my Outlander both fans kick in at the same time.
All the cars I have seen so far ran two fans at a time, if so equipped.It is the speed that is varied. Audi, for instance, uses onemotor to drive two fan pulleys, so it simulates two fans. Other cars use individual motor for each fan which is more reliable. Inlatter arrangement two motors are switched series for lower speed and parallel for maximum blow.