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Discussion Starter #1
Hello,
I was hoping to get a little insight for my issue at hand. I have a 2012 Polaris 500ho and the HOT & check engine light come on as soon as I turn the key. I did take it for a good ride last weekend and cleaned afterwards... and the LIGHTs came on post washing. I have checked all connections, unhooked battery, levels are good, powered fan from alt source.. all looks good. I have unplugged my thermo sensor on the cylinder and the hot light and check engine light goes off.... to me it indicates the sensor is bad???? am I missing something else????

Thanks for any info!!
Squib
 

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Sensor on "post washing"..... to me that says something (wire connecter perhaps) got wet and is conducting. But it could just be coincidence too..... does the fan kick on?

Have you tried blowing dry (compressed air) and applying dielectric grease to the sensor connector? or any other connectors in that loop?

Don't recall how off the top of my head, but I believe the sensor can be resistance tested to see if it's failed...... I'd do a search on that as well.

Good Luck.
 

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Discussion Starter #3
I have cleaned the connections.. No dialectric though... The fan does not come on.. although I only ran it for a few minutes.. I guess I am not sure on exactly what is the "loop"... I believe there is another temp sensor right on the radiator that I see... I am not sure if this sensor tells the fan or if its the one that I am questioning?? the buggy is fairly new this is the first i have had to deal with any issues so I am a little green on the whole workings everything...

Thanks
 

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Discussion Starter #6
So when I unplug my temp sensor on the side of the block the HOT light goes off. I ohmed out the sensor and it read 200ohms. So the ATV is happy with infinity and must lower the resistance as the machine heats up. Does any one know the resistances that the atv is looking for or what a good sensor reads when cold??

Thanks Squib
 

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So when I unplug my temp sensor on the side of the block the HOT light goes off. I ohmed out the sensor and it read 200ohms. So the ATV is happy with infinity and must lower the resistance as the machine heats up. Does any one know the resistances that the atv is looking for or what a good sensor reads when cold??

Thanks Squib
The engine coolant temperature sensor measures coolant temperature. The engine temperature sensor is a Negative Temperature Coefficient (NTC) type sensor, as the temperature increases the resistance decreases.
Coolant passes through the cylinder and by the sensor probe, varying a resistance reading which is relayed to the ECU. This signal is processed by the ECU and compared to its programming for determining the fuel and ignition requirements during operation. The ECU also uses this signal to determine when to activate the fan during operation.
ECT Sensor Test
To quickly rule out other components and wiring related to the ECT, disconnect the harness from the ECT sensor and start the engine. After a few seconds, the fan should turn on and the “Over Temp” indicator should display on the instrument cluster. This indicates all other components are working properly.
Refer to Chapter 4 for additional ECT information. Polaris dealers can test the sensor by using the Digital WrenchTM Diagnostic Software (dealer only).
ECT Sensor Resistance Readings

Temperature °F (°C)
Resistance
32 °F (0 °C)
5.9kΩ± 5%
68 °F (20 °C)
2.5kΩ± 5%
176 °F (80 °C)
323Ω± 5%
212 °F (100 °C)
186Ω± 5%
 

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im having the same issue except I let the bike idle and the fan cycles like its supposed to, the hot light will go out for a min and then come back on. if I unplug the cyl head temp sensor the light goes off
 
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