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Discussion Starter #1
Hi, I am new to ATV repairs and trying to help fix my neighbors 2014 Sportsman 850. His radiator fan turns on as soon as you turn the ignition key on. He replaced the thermistor, it still runs nonstop. We tried swapping relays to rule out a sticking relay. I boiled his old thermistor and saw it change from 2.5 k ohms to 200 ohms, the thermistor is fine, no shorts to ground. I metered 12 volts at the relay coil. I disconnected the thermistor connector on the bike and ran the yellow wire from the ecu through his old thermistor with 2.5 k ohms to ground, the fan still ran. The next move I am considering will be to disconnect the ecu and meter the yellow and violet conductors for open or short conditions (once I figure out how to disconnect it).
The bike also shows a high voltage code for the fan
While following the path of the violet wires looking for the ecu ground splice point, which we haven’t found yet, we were looking at the gear indicator switch which isn’t working on his bike and noticed a tiny amount of moisture in the switch at the base of the pins.
Would anyone have some tips to share in solving this puzzle?
- and no, I won’t quit my day job :)
Thanks
 

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for shits and giggles test voltage at the battery terminals with the machine running @3,000rpm. should read 13.5-14.5vdc. reason for this is to establish the regulator isn't bad and creating issues. ok but your issue is the temp sensor on the head. when it goes bad the fan runs wild, or constantly.
 

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Hi i don't have wiring dia for that model but generally they run a thermo switch (sensor)screwed into the radiator or head and its ON or its OFF so when the engine gets hot its on when it cools its off its not a thermo resistor so you need to find the thermo switch and test for continuity (closed circuit) so when cold it needs to be open circuit if its not open circuit than its stuffed stuck in the on position.
 

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I answered your other post, but I'll duplicate the answer as you duplicated posts:

I do not have the wiring diagram for the 2014 model, but what color wires go the the fan? Org/blk and brn?
 

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Discussion Starter #6
I got to spend a few minutes on it today. While running at a fast idle, I read a very steady 14.5 volts on the battery. I think the regulator/rectifier is fine.
 

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Discussion Starter #7
I checked his original thermistor and it was within the manuals specifications of 2.5 k ohms at 20 degrees Celsius and 200 ohms in boiling water. I think the thermistor is fine
 

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Discussion Starter #8
The next time I work on it we will meter for grounds or opens on the wiring between the ecm and the sensors. The code that it is throwing is 110 3.
 

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Discussion Starter #9
Late-bird, Thank you for your help thus far. I will stay on this post as I think the other post may have been in the wrong section of the forum. I replied to someone else’s thread on the same problem that I found through a search.
To answer about the fan wires, they are blue/white and black to the fan. We think that the previous owner may have replaced the fan at some point. The manual shows it differently and it is correct as per the manual leading up to the fan with orange/black and brown.
 

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Discussion Starter #11
The fan stops when the relay is out. I have confirmed 12 volts energizing the relay coil leading me to think that the ecu has been fooled into energizing the relay to switch the fan on. The voltage read at the battery is fine while the engine is running at 14.5 volts. Next step will be metering my way through the thermistor wiring.
 

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Can you not clear the code from the ecu and it go back to normal till it throws a code again or it may have just sensed a slight out of parameter reading that throw the code causing the problem and it may not happen again i know my 700 grizzly had some codes that i cleared and there not returned but i had found the harness rubbed thru in places . Maybe something like a wire in the harness rubbed thru causing the ECU to think the engine is running hot just thinking out loud.
 

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Discussion Starter #13
Tried a few more things today.
We disconnected the ECU and connected an ohm meter to the thermistor’s yellow wire terminal in the ECU plug and confirmed continuity to the thermistor, then looked for readings to all other pins in the ECU connector block, ground, and positive - all clear.
We moved to the violet wires connector port of the ECU block and repeated the procedure, all clear other than the readings taken back through the gear indicator switch and the throttle switch (which share the violet wire) which gave readings that appear fine.
We disconnected the stator plug and confirmed no short to ground or open readings from the stator.
No change after putting it back together, the fan runs constantly and the quad starts and idles fine but has an odd cough when you throttle up, a roughness similar to having an engine governor.
We tried to clear codes last time we worked on it by disconnecting the battery and holding the cables together for 20 seconds prior to reconnecting them and flashing it up, the code remained.
Can anyone tell me the purpose of the switch that ties in with the throttle, if there is a better way to clear codes, or how to tell if you have AC power causing troubles with the DC circuits?
Thanks, having a hard time trying to decide where to look next
 

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Discussion Starter #14
Probably worth mentioning, found out today, my neighbor has tolerated the fan running constantly but stopped using his quad after upgrading the broken plastic throttle lever with an aluminum throttle lever. He told me that it started running rough when he replaced the lever. I don’t know what the purpose of the switch that is linked to the throttle and would like to know how it should be set up.
Thanks again for any tips
 

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Test the thermistor and ECU logic this way; with the thermistor unplugged, the fan should run - ground the thermistor wire and the fan should shut off - if it does, replace the thermistor - if it runs both plugged in and grounded, replace the ECU or take it to a dealer for diagnosis.

Normally the throttle switch will cut the ignition if the throttle cable sticks and the throttle lever is released. I'm not sure on this model as I can't seem to find it on the wiring diagram.
 

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At this point it my be worth throwing a toggle switch in it to operate the fan manually.
 
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