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Hey guys, new to the forum. Just bought an 08 black/white kfx450r in january and has had a problem overheating up until this last weekend i put some engine ice in it out at the dunes to calm in down a little bit. But anyways my fan never comes on and i'm told its probably the fan relay.. Is there a way to test it before i go buy a new one? probably a simple fix but just wanted some advice. any would help thanks.
 

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Radiator fan is also tied into the water temp sensor on the back of the motor. I just had to replace mine.
 

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Check the fuse.

The relay is difficult to test. You will do better swapping with another and seeing if it will turn the fan on.

To test the relay, remove it. Use aligator clips to hook the thing up to power and ground so it clicks closed. But then you have to use some electrical tape to keep the alligator clips from touching because the space is so close.

Once closed, you have to measure the resistance in ohms across the other two pins. It should have no resistance.

If no click heard or -OL- on the test, the relay is not closing to allow voltage across the points you are checking. If it does close, it should have no resistance. If it has resistance it is bad.

The ones that had been exposed to my bad fuel pump motor had I guess burnt contacts. You could easily hear either close, and both provided voltage all the way to the pump. But not enough amps could cross the relay to actually supply the motor.
 

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Radiator fan is also tied into the water temp sensor on the back of the motor. I just had to replace mine.
Yes and if you unhook from this sensor with the stock ECU, the fan should immediately kick on by default. If not, the ECU could be the problem.

If the fan runs though, it is your coolant temp sensor reading low. This will not throw a code but will cause you to run hot and possibly lean at high temp.

Understand that if there is some output to the ECU, rather a lie or not, the ECU takes it as truth and will not enrich fuel or kick on the fan soon enough.

I have been fortunate that mine went bad the other way, causing enrichment and the fan to come on early, so my quad appeared to run cold and rich.
 

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Mine was the opposite where it was running super hot, and the fan wouldnt kick on, and as soon as I let off the throttle from high rpms and pull the clutch in the quad would die. Tested it yesterday after the new sensor fan kicks on and no more cutting out after I let off from full throttle.
 

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Mine was the opposite where it was running super hot, and the fan wouldnt kick on, and as soon as I let off the throttle from high rpms and pull the clutch in the quad would die. Tested it yesterday after the new sensor fan kicks on and no more cutting out after I let off from full throttle.
Glad you are fixed man.

This whole thing is a scary thought though, no?

I am very thankful mine has never went your way but I know of cases of it.
Could take out a motor if not caught in time.
 

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Mines doing that right now runs hot and never kicks on pulled the plug off the temp sensor fan kicks on guess its the sensor
 

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Ok mines not fixed still throwing the temp light running super hot, think its time to pull the motor. Duster might need a custom map for a procom. I've changed sensors, tested my tps nothing is fixing my issue. So next is compression test and valve clearance but I still don't think that's going to solve my issue it seems to be an electrical problem. I'm running out of ideas. Full motor tear down and build and replace everything might be in order.
 

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OK... I just wrote in another thread that I wish we could find an aftermarket alternative here that would work and be trustworthy.

I guess this lays an exclamation point on that.

I doubt it is in your motor. I have had more experience than I wanted in this electrical stuff. We will find it.

Do the compression test and get a good look at your plug while doing it. We will talk tonight on this because I doubt you have engine issues. Just a gremlin.
 

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Thanks Duster ill pm you my number and maybe we can figure out why this thing is giving me issues.
 

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Question the fan sensor is on the back of the fan? I pulled it of and fan didn’t come on. I checked the fuse in orange cover. Fuse is good.
 

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Can I wire a direct power switch from the battery? Does it have to be in series.
So I connected direct power to the fan, so I can run at all times. I noticed the fourth red light is on. Is this light the temperature switch behind the engine? Because it’s in series with the fan?
 
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