While riding today my coolant resevior started to overflow and I was running hot. I noticed the fan was not on and I was able to get back to the house. Inspected unit and did not notice any leaks in radiator. Do these things have thermostats on them? What triggers the fan to come on? Any light shed on the situation would be great. Thanks in advance.

 

if you do a search on overheating you'll find dozens of pages on this. yes it has a therostat. the sensor is what turns on the fan when it gets to the hot temp. test your fan to see if its working.