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Discussion Starter #1
Hey guys. New to the forum but not to riding or to Polaris. I've been riding and wrenching on bikes, quads, and SXS's for over 35 years.

I bought an old 2000 Sportsman 500 a couple months ago to use for hunting. After repairing a couple of relatively minor issues, it runs and rides great but I cannot get the fan to work properly.

Here's what I've checked so far.....

(1) The fan works fine (checked it with a jumper)
(2) The circuit breaker is fine (unless there is another one that I'm not seeing).....verified voltage in and out with a meter
(3) The coolant sensor (on the radiator) is fine, but I replaced it anyway, just to see if there was any change and there was none. Interestingly, when I jumper wiring harness that the coolant sensor plugs into, the fan will come on.
(4) The only thing that I haven't checked or replaced is the temp sensor on the cylinder. From what I've read and based on my experience with other Polaris engines, the fan should default to on (fan should run) on when I unplug that wire.......but it does NOT come on when I unplug it.

Where do I need to go from here? I was going to replace the temp sensor, but because the fan doesn't run when I unplug that wire, I really don't think that's the issue. What am I missing?
 

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The sensor on the engine is for the temp indicator - ground it and it should indicate hot (hot light comes on) - you have a bad sensor in the radiator, the coolant level is low or it has not gotten hot enough for the fan to turn on - if you jump the sensor and the fan runs you have just proved there are no open fuses or breakers, you have 12V and the ground is good.
 

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Discussion Starter #3 (Edited)
.........- if you jump the sensor and the fan runs you have just proved there are no open fuses or breakers, you have 12V and the ground is good.
Thanks for the response. That's what I thought. Just wasn't sure if there was something in the ECU that might keep it from coming on.

I'll ground the hot light temp sensor and check it when I get home. Am I not correct that it should default to on (fan running) when I unplug that temp sensor (the one located on the cylinder)???

The sensor was brand new and the coolant was DEFINITELY full (and bled), so I don't think that was the problem.

It's "possible" that I may not have gotten it hot enough to cut the fan on after I replaced the temp sensor on the radiator. I ran it for about 2 miles in low range and then let it idle for probably 10 minutes. The radiator felt hot to the touch, but possibly not hot enough. I'm just afraid to let it get TOO hot before shutting it off.

Other than this last issue that I have to resolve, it looks and runs great, and had very low hours when I got it. Luckily the previous owner was smart enough to recognize that the fan wasn't running and had hot wired it to come on as soon as the key was cut on.
 

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They didn't start the fan on default in the ecu until 2004.5-2005.
And yes it is a good idea to verify the temp. light as working properly, it's often overlooked. If it's not working ,normally the lil bulbs are burned out.
 

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Discussion Starter #5
They didn't start the fan on default in the ecu until 2004.5-2005.
And yes it is a good idea to verify the temp. light as working properly, it's often overlooked. If it's not working ,normally the lil bulbs are burned out.
That's good to know. I'll check out the hot light tonight. Thanks!
 

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Am I not correct that it should default to on (fan running) when I unplug that temp sensor (the one located on the cylinder)???
That is not correct for your model - the newer models use a single sensor and if the sensor fails, the fan defaults to 'fail safe mode' and runs continuously - yours has one sensor to control the fan and one sensor to activate the light - the fan sensor closes before the hot sensor does.

Running in low may not generate enough heat to cause the fan to come on - just being in motion is enough to prevent the fan from coming on. I don't like to let an engine idle for more than 5 minutes, but when testing the fan, you have to let them idle in a shielded area (minimal air movement) until the coolant boils or the fan comes on. If the coolant boils, then obviously the engine is overheating, but the fan usually does not turn on until about 192 degrees. Boiling coolant will not hurt the engine, but continued operation while the coolant is boiling may cause damage.

The cooling system usually has about a 8 lb pressure cap. Each 1 lb increase of pressure raises the boiling point of water about 3 degrees. Water boils at 212 at sea level - increase the pressure by 8 lbs and water then boils at 233 degrees - add antifreeze to the water and the boiling point is raised even more - a 50/50 mix of antifreeze at sea level boils at about 226 degrees - put 8 lbs of pressure on a 50/50 mix and the boiling point rises to about 248 degrees - Polaris specifies a 60/40 mix which means the boiling point is elevated above about 253 degrees.

Engines will perform fine at temperatures much higher than that without damage. My air cooled TRX400EX will heat the oil to near 300 degrees without damaging the engine. Liquid cooled engines are a bit more fragile as the oil might get to 300 degrees while the coolant is near 250 - remove the coolant by boiling it away from the surface of the metal it is in contact with and the temperature sky rockets to over 400 degrees in seconds - oil boils at around 300 degrees - when the temp of engine parts exceeds 300 degrees, lubrication fails and engine damage occurs.

You will have to let it run at least till the coolant boils or the fan comes on to test the sensor.
 
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