So I bought a 1990 Polaris 350L 2X4 the other today from an 18 year old kid who basically rode it into the ground and left her for dead. I went over it pretty good and found quite a list of repairs needless to say. Anyway I have no manual for it yet but after fixing all the little things with it I was trying to set up the carb and while I was playing with it the "hot" light came on but no electric fan? I see there is a thermistor on the right side of the jug with 1 wire coming out of it. I am assuming that this is the ground side switch for controlling the fan. Can anyone that has the manual tell me if I am correct? Charging system is working great and charging around14 volts revved up. I'll probably just hot wire the fan momentarily to see if it works tomorrow.

 

So I drained the rad and hot wired the fan momentarily to make sure it works. Fan works great but as I was unhooking the electrical I found power to the fan is interrupted by a switch in the top of the rad. I believe this is my culprit. Still not sure how the switch in the cylinder head comes into play on this one here but I'm pretty sure it has something to do with the "hot" light in the dash there. Anyway tomorrow I will bypass the rad switch to make sure that is the problem.

 

Sensor on the head is just for the hot light only.. The radiator sensor completes the ground path for the fan to kick on. Common for these sensors to short out if the coolant level gets below their level. Go to any auto store and match up a two pronged sensor to yours and wire it up to your harness for around 20 bucks or less.Needs to be a 175 degree fan sensor as the hot light kicks on at about 205 degrees. The oem wired sensors are NLA. PLUS there is a 10mm bleed bolt on top of the head close to the temp sensor. Open it up and let coolant flow out and it will also remove any trapped air pockets that can cause over heating. People forget about doing this on the 350/400 engines.

 

I am having the same issue. 1990 Polaris 350L 4x4. Temp Light comes on after a little bit. and I do not hear the fan running ever. Is the sensor on the rad my culprit as well? I need help fast on this so any answers are appreciated