My 96 e300 temp gauge usually operates at 100 degrees C, lately I noticed that the auxilliary fan does not turn on when the temp gets hot. It will operate for a few seconds then cut off - unlike before when it will keep on for a while. From what I can see, it seems that the switch tells it to turn on but ir just won't as if something is stalling the fan. Can someone tell me if the auxilliary fan is the problem? Or is there a way I can check if this is a faulty switch or sensor ? Or can someone tell me how to diagnose the problem properly?