I'm working of a friend's Sportsman 500 H.O. carbureted model and it flashes "HOT" on the display and the fan will not run. From my reading and trouble shooting so far I think it's an electronic module between the steering and radiator and is under a recall for this but before finding that info out I checked the resistance on the temp sensor mounted on the cylinder of the engine and got a resistance reading of 1,570 ohms when engine cold ambient temp around 85°F. I started the motor and watched as the resistance dropped and after a few minutes and engine pretty hot it stabled out around 360 ohms. I have a Clymer manual that says the sensor should be reading around 37K ohms at 68°F so just wondering if the temp sensor is OK. For one thing I've only ever seen sensors climb in resistance with temperature increase and this one is doing the opposite. I disconnected the temp sensor and applied 37K ohms to the wires going back to the harness and it made no difference, display still flashing "HOT". I just mainly want to ensure the temp sensor is good before taking it in to the dealer for the recall work, rather pay $73 for it online the best price I could find over his $135 plus labor to put it in you know.

Edit: I don't know why rts is on the end of my title heading but I can't edit it. It's just a plain 500 high output, not some fancy "race track special" or whatever "rts" could stand for LOL
Edit again: Any IT guys please explain how the "rts" I typed into Sportsman got delayed and tagged onto the end of H.O.

 

This temp sensor does the opposite of what you're thinking. Resistance does drop on this one as it gets hot because when it reaches a certain lower resistance level it completes the ground path for the ecm module to kick the fan on. If the ecm hasn't been changed ,still has the black Chinese module,just take it in and have the updated ecm installed free of charge. Should solve the problem. Rarely ever had to replace a sensor. Polaris Industries Expands Recall of ATVs Due to Fire Hazard | CPSC.gov

 

Thanks for all your contributions Old Polaris Tech. I found the recall info during a search and it was you telling about the recall so you saved me some time and my friend, the owner of the quad, some cash.

I have called a local dealer which said the VIN I gave them does fall under the recall and doesn't show up of ever having been done. I'm taking it in today for this work.

The temp sensor certainly works backwards from all I've seen but glad to know it's doing what it should.

Thanks again.