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Discussion Starter #1
I have a 1998 Polaris Sportsman that the radiator over heats after 10 minutes on idle. I checked water pump spins when motor running. Replace fan, radiator and heat sensor. I jumped out the fan and works no issues.
Where do I go from here? I've replaced everything
 

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Is there a thermostat in the cooling circuit? And test your radiator cap. If it doesn't hold the lower pressure, it can cause an overheat.
 

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Discussion Starter #4
Cap and radiator new. I did also replace thermostat. Only 800 miles you think head gasket ? Any way to be sure before I do it
 

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Pressure test the system.
 

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Discussion Starter #6
Shouldn't the fan kick on is the fluid gets a temperature I ran the fan manually and it never overheated the fan kept it cool
 

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Discussion Starter #7
Thank you for your help that might be out of my league I can fix certain things but getting into a head gasket might be over my head
 

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So if I'm understanding you correctly the can does not come on unless you override it to run??
 

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Yes if I jump off the fan it comes on it keeps the radiator cool no reheating could it be a bad heat sensor I just don't feel it's a head gasket
 

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Discussion Starter #10
I just ran it for 30 min witty jumping the fan never overheat. Plug back into the heat sensor didn't turn on and after 10 minutes the radiator overheated again
 

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We are all guessing blind and in the #1 post you stated that you replaced the sensor so I just immediately presumed you had tested the sensor and it is working.

Now if it does not overheat with the fan running, we got to get to the specifics of the wiring. Al we know is that it's a 99 Sportsman - is it a 335 or a 500? They are wired differently. I'll check the wiring and tell you what needs to be tested. Maybe give me the VIN or model number off the frame and maybe I'll tell you things you don't know about it.
 

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It's a 500 I will go get the Vin number this might sound crazy but can you test the heat sensor by taking it out and putting a heat gun to it I really appreciate your help
 

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Here's what the VIN reveals:

Model Name - SPORTSMAN 335G
Model Year - 1999
Model Number - A99CH33AA
Purchase Date - 5/20/1999
VIN - 4XACH5OAX11A016146
Engine Serial Number - 9915598
Factory Warranty
Start Date - 5/20/1999

So - the model number says it is a 99 335 and Polaris identifies it as a 335, but the VIN identifies it as a CH50 (500 cc) instead of a CH33. The unarguable part is that it is a 99 instead of a 98.

Now, it has to be a 500 because the 335 was oil cooled - test the fan switch by unplugging it and jumper the two wires (red/wht to org/blk) of the plug together to see if the fan runs. Both the key switch and the handlebar switch have to be in the run position for the fan to have power. If the fan runs when the wires are jumped, the thermo switch is bad. If the fan does not run when the wires are jumped, check for 12 volts on the red/wht wire. If the red/wht wire has 12v, leave the wires jumped together and check for 12v on the org/blk wire at the fan - no voltage, repair the org/blk wire, voltage, repair the ground to the fan motor (brown wire).

To test the thermo switch, connect a continuity tester to the two terminals and suspend the sensor in a container of water - heat the water and just prior to the water boiling, the switch should have continuity. It will open again at about 180 degrees.

BTW, there are 2 thermo switches on the 500 - the fan switch is in the radiator and the hot light switch is on the engine near the thermostat housing. Fan switch has 2 wires - light switch has one wire (blu/wht).
 

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I agree sounds like a fan switch, also sort of dumb question but is all the air out of the system? I replaced the fan switch on one this summer and had a hell of a time getting all the air out.
 

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Manual should give test parameters for the switch, resistance in ohms and a set temp. Also if the switch checks out then to my knowledge the ECU could be faulty. But that to be determined.
 
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