I have a quick question on trouble shooting the Fan on this trail boss. As soon as I turn the key on the fan is running. Recently rebuilt the motor and ended up breaking the sensor trying to remove the wire coupler. Currently have a second trail boss I picked up to rebuild and took that sensor in the head and it just runs. Is there any other sensors on the machine or is it just the one?
Thanks

 

Sensor on the head is temp sensor for the hot light. The fan sensor is a two pronged sensor at the top of the radiator that when hot closes it's contacts and provides a ground path for the fan to kick on. If the fan's running all the time,the sensor has shorted.You might want to consider this one for 25 bucks since they're NLA from dealers and online sources.Cheaper than what they normally were..Polaris Sensor Thermal Harness P N 4110099 1990 1995 350L 400L | eBay Or you could try to match up the threads on your old sensor with a two pronged sensor from a local auto supply.

 

Thanks for the reply! Looks like I will be purchasing one!

 

I know this is 5 years late, but sometimes people will wire their radiator fans directly to the key when the sensor goes bad. My buddy has had quite a few different ATVs where people have done this. The fan runs any time the key is on.