Looking for help with the following issue. Not sure what to try next.

I am having a problem with my 2004.5 Sportsman 500 that I can't seem to correct. After the bike gets warmed up, the "HOT ENGINE" warning will intermittently flash on the speedometer. There is no evidence that the bike is overheating - sometimes the fan will kick in while the display is flashing "HOT ENGINE" and other times it won't. At this point, unplugging the thermistor will always trigger the fan to turn on. The thermistor resistance is always well above where it should be for the hot engine. Thermostat has been changed, ECM has been changed, water pump impeller has been checked, thermistor resistance has been checked in a pot of water as it heats, air has been bled from rad. Wiring harnesses have been inspected from speedometer,ecm,thermistor,fan. The only other thing is that this began happening after the fan was replaced with an aftermarket unit. Is it possible that the fan is not compatible with the ECM? I know unplugging the fan motor also causes the light to come on. Any help would be appreciated

 

Dollar to a donut another ecm failure.. Ecm controls the fan,charging,battery protection circuits,auxiliary power,the hot light,plus contains the solid state circuit breakers. One part of the ecm can go out,other sections can still function,or it can cut power completely to the machine. Sorry got a habit of speed reading that gets me some times.. Rather than blame the fan,I'd try to bleed the cooling system again even if you have already. Jack the front end up and leave the radiator cap off. It make take some time for the air pockets to be removed.If that doesn't help then it's not impossible to have another faulty ecm.

 

ECM was replaced with new OEM from Polaris. Same problem???

 

Read my post again,I saw my mistake... I've thought I've had all air removed from machines when I bled them only to have similar things happen with the hot light and fan. Tried the bleeding process again and solved the problem. Hope that's all that's needed..

 

Lol I did the same thing with my reply. I can try again bleeding air but I have done it 3 times now with front of bike lifted. If it was air, wouldn't I be getting low values on thermistor resistance? I don't see any other sensor wired to ecm

 

Hoses should be warm,resistance should drop on the radiator sensor. When the radiator sensor bridges,it completes the ground path for the fan to kick on. Check that you have constant power on the fan hot wire also. If the sensor is operating correctly,fan power wire is hot,still can't help but think either air pockets or a faulty new ecm. If the replacement fan is an 11 inch Spal as most are,it should be the source of the problem.

 

That's just it. I don't see any sensor in the rad - only the thermistor on the side of the cylinder that connects to ECM. I think I saw that the ECM switches the ground to the fan when it calls for it to run if I remember correctly.

 

ECM will also trigger this hot light if I unplug the fan. Tried checking fan resistance but it fluctuates all over the place if you slightly touch fan blade. Not sure if this is normal as I don't have another fan to compare to. I thought ECM may be interpreting as open circuit fan and generating hot alarm as protection.

 

Oh yes,,, forgot again on this model that the ecm does do away with the sensor. It's all internal. The more you post,the more it sounds like a faulty ecm module. Controls the fan,controls the hot light. 2004.5 is basically a 2005 model. Plus before you go too far I'd do a coolant pressure check as simple things like a leaking 13 psi cap or even a warped remote filler neck can have you chasing your tail.Must hold 10 psi with no drop.

 

ECM will also trigger this hot light if I unplug the fan. Tried checking fan resistance but it fluctuates all over the place if you slightly touch fan blade. Not sure if this is normal as I don't have another fan to compare to. I thought ECM may be interpreting as open circuit fan and generating hot alarm as protection.