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Discussion Starter #1
I left from riding the other day, and drove home in the 30 degree weather for a solid 45 min. when i unloaded i heard the fan running, with no key in the ignition and it had plenty of time to cool down. Only way to kill it was to loosen the battery cables. What could cause this?
 

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Stuck radiator fan relay....

It is the one with the blue wires.
 

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Yeah, it is kind of stupid the way I see it, but what do I know right?
I'm no electrical engineer.

The fan relay is connected directly to battery power BEFORE the key switch.
So if the relay sticks the fan is tripped on even with the key off because the run power is supplied before the key switch.


To test the thing, simply unplug the relay.
Then borrow one from one of the two with the brown wire running in the bottom of them.

In other words swap them.

When you hook the battery back up after the swap, the fan should not run if it is the relay that was stuck.

And if it is still stuck, it should now turn the starter in some way that it should not.
In other words it might try to start without the clutch pulled in while in gear or something.


That will let you know if it is indeed the relay (hopefully) and not something more complicated.
 

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Discussion Starter #5 (Edited)
well, i done as suggested and swapped the far left one with blue wires(#1), with one from the far right (#4) with brown, same results, and then with the other one (#3) with brown, fans still runs on its own. Thanks for the help guys, what else you think it could be?

When i put the key in and turn the ignition on, the fan starts spinning for about 3 seconds then goes off. Then i take the key out, and within about 10 -45 seconds, the fan will kick back on. I really need help, i have to undo the battery each time I put the kfx up now.
 

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doesnt temperature tell the relay to turn on.... could be stat.
 

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Well, I hate to hear this...

Check the wires there really well for wear. I really hope now that you find the wires rubbed and touching each other. Also check your frame ground good (under seat).

If not, you are going to have to unhook your ECU and see what happens. I really fear your ECU has failed.

See, the ECU collects the data from the coolant temp sensor and decides when to trip the relay to cut on the fan. In reality what it does is supply a ground source to the relay.

Say what? Want to understand how that works? Just look at the 4 wires going in the plug.

Pink/Blue = Ground source controlled by ECU
Blue/White (#1) = Throw voltage

Blue/White (#2) = Supply voltage to relay .....(yes these come right off the same source)

Blue = Out wire to supply voltage to the fan

What happens is... the ECU decides the fan needs to be on, so it trips and supplies a ground source to the Pink/Blue.

The voltage on the White/blue (#1) is there and flows to the Pink/Blue because the ECU supplies the ground path. When it tries to flow to the Pink/Blue the voltage "energizes" an electromagnet. This magnet draws the switch in the relay closed (throw voltage).

When the relay is thrown closed... this makes the connection between the White/Blue (#2) and the blue wire that runs out to the fan.

Using the same wire pigtailed into two is a little strange and makes it harder to understand, but I think you can see how it works. And with that said, if it is not the relay and not the wires being bare allowing voltage to bypass the relay.... well then the only other explanation is a bare Pink/Blue touching somewhere supplying ground, or a faulty ECU.

Nothing else is involved with the key off.

And with a stock ECU, a broken connection to the coolant temp sensor will cause the fan to run continuous. All you have to do is unplug it and the fan will run always with the key on.
 

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Clay, are you near me or another KFX owner?

If you unplug your ECU with the key off, it should stop running the fan.
(let me know what happens)

Did you buy this KFX new?

And if you are close to me or another KFX owner, an ECU swap is in order.
This way you can make sure the ECU is the problem 100% before buying.
(buy a Procom ECU)
 

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Clay, are you near me or another KFX owner?

If you unplug your ECU with the key off, it should stop running the fan.
(let me know what happens)

Did you buy this KFX new?

And if you are close to me or another KFX owner, an ECU swap is in order.
This way you can make sure the ECU is the problem 100% before buying.
(buy a Procom ECU)
duster have you applied for a job at kawi engineering yet? you could be their tech pro!! really hope some wires are touching or is there any chance the sensor is faulty?
 

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duster have you applied for a job at kawi engineering yet? you could be their tech pro!! really hope some wires are touching or is there any chance the sensor is faulty?
I wish they would offer me a job...
I'm back to work now, but doing slave labor in a factory.

I'm hoping the Blue/white and Blue have rubbed together and are letting voltage bypass the relay... as the blue/white and relay get their power before the key switch (stupid). Or the Pink/Blue has rubbed against the frame, supplying ground to the relay and allowing power to flow through to the fan.

It's just not sounding like that though... sounds like the ECU... grrrrr...


The temp sensor gets it's power source from the ECU, and the ECU should not supply that power, nor read the return, nor trip the fan with the key off.


HEY... A BAD KEY SWITCH IS POSSIBLE TOO... CHECK IT!!!!

Put it in neutral so the light is on and turn off the key, light should go out... or unhook the key switch and check it with a meter... continuity, should only beep in the on position.

A hot motor + key on or faulty will cause the fan to cycle also. Check the switch or connect the battery back when the engine is cold and see what happens.
 

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Page 444 PDF service manual...KFX450 Service Manual - Kawasaki KFX450 Forum :: KFX450HQ.com

You'll noticed that the Fan fuse doe not go through the Key switch....The white wire is continuous power from the battery...

The P/BL wire is the switch leg or signal wire that turns the fan on/off via the ECU..

Try un-plugging the water temp sensor....and turn "on" the key...and see what occurs???

The key ignition turns the water sensor on & off...via Brown wire from the key ignition...The white wire is continuous power from the battery...

So technically the ECU is bad if you turn the key off, which turns off the water temp sensor, and the fan remains running...
 

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Right... so it has to be....

1- Bad key switch not staying "off"
2- Pink/Blue worn through & grounding to activate relay
3- Blue/White & Blue rubbed together and worn through, bypassing the relay
4- Bad ECU
 

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Right... so it has to be....

1- Bad key switch not staying "off"
2- Pink/Blue worn through & grounding to activate relay
3- Blue/White & Blue rubbed together and worn through, bypassing the relay
4- Bad ECU
Yes !! except, the pink/blue is a positive wire, that activates the fan relay and if it shorts to ground, it will fry the circuit in the ECU & relay coil windings...And pop/burn the fan fuse....

I say it's a bad ECU...That's why it's not coding the F.I light....
 

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Discussion Starter #15 (Edited)
ok, when i unplug the sensor and turn the ignition to on, the fan starts up and the FI light stays on red constantly and it will not crank. when i turn off the ignition the fan is staying off with it unplugged. So to get it to crank i must plug the sensor back up.i live in MS and no one has a kfx450 anywhere around, so i cant pull and test from anyone else.
 

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Right... so it has to be....

1- Bad key switch not staying "off"
2- Pink/Blue worn through & grounding to activate relay
3- Blue/White & Blue rubbed together and worn through, bypassing the relay
4- Bad ECU
ok, when i unplug the sensor and turn the ignition to on, the fan starts up and the FI light stays on red constantly and it will not crank. when i turn off the ignition the fan is staying off with it unplugged. So to get it to crank i must plug the sensor back up.i live in MS and no one has a kfx450 anywhere around, so i cant pull and test from anyone else.

And when you hook up the sensor back up...Does the fan continue to run...after you turn the key Off..????

If so...
Dis-connect the water temp sensor "again", and take a 22 gauge solid wire and loop the orange & BK/BR wire together....

Turn the key on then off...and does the fan remain running????

If so...
You have constant power on the pink/blue wire keeping the relay activated...

And that is the ECU that controls the pink/blue wire switching of power on/off ...
 

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ok, when i unplug the sensor and turn the ignition to on, the fan starts up and the FI light stays on red constantly and it will not crank. when i turn off the ignition the fan is staying off with it unplugged. So to get it to crank i must plug the sensor back up.i live in MS and no one has a kfx450 anywhere around, so i cant pull and test from anyone else.
OK so you have switched the relays. Not the relay.

Do your dash lights go out when you turn off the key????

From what you are saying here, you either have a bad key switch or a bad ECU.

I myself have a bad water temp sensor I need to replace. I can tell you with certainty there is no power running through the water temp sensor with the key off (and working). And I can also tell you with certainty as before, your fan will run continuous with the key on and water temp sensor disconnected. It's the default safety of the stock ECU.

If your key switch is working properly, your fan should never run with the switch off. And if it does run with the key off, it's either the ECU turning it on or wires shorting together or to the frame.... but your latest post there does not indicate bad wiring.

With that said, you can buy a new water temp sensor if you like, but I do not believe it will solve your problem.


I also do not believe the pink wire is a power wire. I believe it is a ground. But do this final test if your neutral light and stuff does not burn key-off....

Plug everything back up so your fan runs with the key off.
While it is running, unhook the fan relay.
Put your meter on DC.
Place the red lead in the terminal for the pink wire.
Place the black lead to the frame.
(do you have voltage?)

If no voltage, set your meter to the continuity beep.
Red lead again in the terminal for the pink wire.
Touch the black lead to the frame.
(do you have a beep?)
 

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For the record guys, I have always thought the fan switch in the ECU was "the source" of the battery drain issue. In other words, I think this is the flukey circuit that malfunctions.

I just think this guy happens to be the first one with a severe case of it, and also the first one to catch it in action.

I think when you park her and walk away, sometime that night this might happen and run your fan until the battery goes low, and then it shuts off. Kinda like the tree that falls in the woods when no one is there to hear it.....

Just stupid stupid engineering from Kawasaki to allow things access to direct battery power before the key switch. ECU, Fan Relay, Fuel Pump Relay...
 

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For the record guys, I have always thought the fan switch in the ECU was "the source" of the battery drain issue. In other words, I think this is the flukey circuit that malfunctions.

I just think this guy happens to be the first one with a severe case of it, and also the first one to catch it in action.

I think when you park her and walk away, sometime that night this might happen and run your fan until the battery goes low, and then it shuts off. Kinda like the tree that falls in the woods when no one is there to hear it.....

Just stupid stupid engineering from Kawasaki to allow things access to direct battery power before the key switch. ECU, Fan Relay, Fuel Pump Relay...
(I also do not believe the pink wire is a power wire. I believe it is a ground.)

The ECU grounds the Pink wire by a electronic internal switch to a resistor ground...It draws power through the relay, Does not send power through the relay coil windings....And the pink wire is positive (switch leg) until the ECU grounds it (internally) through a resistor..

And if the pink wire is shorted directly to ground with-out resistance, will burn the relay coil, or ECU switching circuit....

(like the negative pulse/fly back) of the ignition coil Bl/w wire....

The Black/Brown is the sensor resistor ground wire...4~6K ohms

The Black/Yellow is the fan motor negative battery ground...0 ohms

Page 444 service manual PDF...or 16-52 electrical system...
 

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Discussion Starter #20
well after unhooking all the relays, temp sensor, and ecu, getting mad and plugging it all back up, it has mysteriously fixed itself. Unplugging the ecu and hooking it up again, made everything work again.........for now.

thanks a ton for all your help
 
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