Okay I have a 05 Polaris sportsman 500 HO. I bought it used and when I bought it the previous owner had the radiator fan wired up to a switch. Every time you turn the key on even when it was cold it would flash hot. I replaced the ECM and bought a new radiator fan. The new ECM fixed the hot flash and the old fan would kick on when it got hot. The old fan was really noisy and the bearing seemed shot. When I put the new fan in when it gets up to temperature the fan will barely kick on and off and never fully come on. When I disconnect the temperature sensor on the side of the block it will kick on and off a couple times and then fully come on. Has anybody had this happen before and where do I need to look or what do I need to try to fix this? Thank you for any help.

 

Sounds like the actual sensor is bad and not sending the correct signal to the fan.