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Coling fan electrical problem #HELP

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Hi all, I am new to the site, had a WR250R now for nearly a year and really enjoying it.   I have carried out a few mods so that it fits me better, mainly lowering and seat scalped a bit, the only thing I would moan about is its weight when I have dropped it a few times on trails.

I need some help with an electrical problem with the cooling fan, not long ago it wouldn’t come on and the engine was boiling so I eventually diagnosed the problem to a corroded terminal in the relay, I cleaned it and put loads of Vaseline around it, ran a check on the ECU 51 (fan relay)  and it activated 5 times as it should – great I thought.

Next time out riding, every time the fan comes on so does the ENGINE WARNING LIGHT, fan goes off, amber warning light off. Another problem it didn’t have before is that when the engine is off/ignition on, the fan wont run, as soon as engine started again, fan runs along with the warning light.

I have cleaned the GREEN overheat sensor, played with the ECM but no difference, anyone gotta an idea??

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Recommend an ECU cold reset.  Disconnect battery ground wire and jump it to the positive cable.  This shorts out the power lead to the ECU and allows any capacitors to discharge.  After 15 minutes, reconnect as normal.

 

If this doesn't work, possible that the fan is drawing too much current.  Put an ammeter in the circuit and post back what you get.  I will then compare it to mine and let you know.

Edited by BluePill

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Thanks for that, is that a wise thing to do, it wont blow up the ECU?

 

I forgot to mention it comes up with fault code 21, but the last time I tried it registered a fault but no code!!

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Thanks for that, is that a wise thing to do, it wont blow up the ECU?

 

I forgot to mention it comes up with fault code 21, but the last time I tried it registered a fault but no code!!

By disconnecting the battery negative cable you are removing the supply voltage to the entire bike.  By connecting the negative cable to the positive cable, you are creating a short circuit at the input of the ECU.  This is a the standard way of doing a cold reset, because any capacitors in the ECU will be able to discharge and completely clear all temporary memory.  When you re-connect the negative to the battery, you restore power to the ECU and it can reboot.  Note that it is not necessary to remove the positive cable from the battery, because no power can flow anywhere with the negative cable off.  It is just the same as removing BOTH CABLES and shorting them together, but it saves a step.  You NEVER jump the connection between the cables without at least one disconnected because that would short the battery and that's a big no no.  Hope this makes sense.

 

Excerpt from Honda Service Bulletin:

 

Before Replacing Electronic Components, Try These Tips Many of the electronic components in automobiles have computer chips. Besides ECMs/ PCMs, youíll find them stashed in audio units; speedometers; odometers; clocks; climate control systems; control units for ABS, TCS, ATTS, and SRS; security systems; keyless remote transmitters; and multiplex control units. The downsides of all this high-tech stuff are software glitches or bugs, and vulnerability to voltage spikes. And if that isnít enough, static electricity, lightning, ultraviolet light, strong magnetic fields, radio waves, and radar can make a software bug even worse. Before you replace a suspected electronic component, try these tips first. They could spare you unnecessary replacement. ï Disconnect the positive and negative battery cables, and touch them together for a few minutes. This forces all capacitors in the component to drain, which clears and resets the computer chip. If a software glitch is the cause, resetting the chip this way is usually as effective as installing a new component. ï Unplug the connectors from the component, wait a few minutes, then reconnect them. If a poor connection is the villain, disengaging and engaging the terminals in the connector cleans contact surfaces and usually fixes the problem. While you have the connector unplugged, look at the pins and terminals for signs of contact. If you have any doubt that things are connecting properly, remove the female pin and use it like you would a feeler gauge to check the contact. If terminals are damaged and need to be replaced, see the article ìNew Terminal Inspection Feeler Tool Set,î in the August í00 issue of ServiceNews. 

Edited by BluePill

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PROBLEM – FAN TURNS ON WHEN ENGINE IS WARM (as normal) BUT THE ECU AMBER LIGHT COMES ON AT THE SAME TIME AND WHEN THE ENGINE IS CUT THE FAN STOPS EVEN WITH IGNITION ON.

Today I managed to spend some time working on the bike –

Battery terminals good

• Cleaned the relay and used dielectric grease

• Battery is reading 12.5v

• Temp sensor – I think that has to be working as the fan comes on along with the ECU light when the engine warms up so I haven’t made a separate test on it.

• The earths seem fine

• Swapped the headlight relay for the fan relay and vice versa – both relays work ok in lights and both throw up same ECU light on with fan.

• Disconnected the battery and held + and – together to discharge the capacitors (cold reset)-THIS THEN BROUGHT UP ERROR CODE 21 iso OF 0, but after subsequent running of fan it displays a 0 error code

• 21---Coolant temperature sensor, open or short circuit detected. • Open or short circuit in wire harness. Defective coolant temperature sensor. Fault detected in ECU

Any more ideas gratefully accepted.

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Can anybody tell me if the TEMP SENSOR is the sensor with the green plug attached to it at the rear the engine - when I short this out it gives a RED OVERHEAT LIGHT.

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Yes, coolant temp. sensor has a green connector with 2 black wires.  It is at the rear of the cylinder.  Based on everything you posted so far, it is likely that the CTS failed when the engine overheated.  This is not uncommon. The thermostat can also be damaged from severe overheat, so a good idea to replace that also.  If it sticks closed you will overheat again

 

The ECU monitors sensors for outputs that are "out of range".  If the CTS is sending "out of range signals", the code 21 will set.  Spec. for the resistance of the CTS is 2.3K to 2.6K ohms @ 68 degrees F. and 310 to 325 ohms at 176 degrees F.  You can test easiy by unplugging the green connector and attaching meter leads to the "prongs" of the sensor.  With the motor "cold" (i.e. somewhere around 70 degrees) you should see the resistance around the specified 2.3K to 2.6K ohm reading.  Now start the engine and let it warm up.  Monitor the resistance for a smooth decrease in resistance to somewhere around 300 ohms when it reaches operating temperature.  If at any time the resistance jumps quickly rather than changing smoothly and gradually, you have confirmed a bad CTS.

 

Here is a link to a video I made when testing a bad pressure sensor: 

 

Although it is reading voltage vs. vacuum, the same principle of a sudden jump on the meter is seen when the vacuum reading is between 10 and 15.  This is what you want to look for.

 

IMPORTANT:  Because the CTS is disconnected from the ECU during this test, you can expect a fault light.  Because there is no valid signal, the ECU *MAY NOT* turn on the fan, so be very careful that you do not allow the motor to overheat.  There *MAY BE* fault logic that the ECU uses when it lacks a valid CTS signal.  That *may*  make the fan run constantly or cycle on and off.

 

I hope that this makes sense.

Edited by BluePill

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Many thanks, would the fan still come on and off appearing normal with the temp sensor playing up.

Now I know where it is I will try your idea. Just away for a few days so will update later.

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Many thanks, would the fan still come on and off appearing normal with the temp sensor playing up.

Now I know where it is I will try your idea. Just away for a few days so will update later.

  Can't say for sure exactly how the fan will operate with a bad signal.  

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Had a day working on the bike – couldn’t get wires to the CTS (cooling temp sensor) in situ so took it out and rigged up some wires to it

and put it in a frying pan with water and heated it up, it started at 2.3Kduring the first 2 sessions it threw a wobbly at 540ohms and second attempt at 375ohms, thereafter it performed without a problem for another 5 sessions so don't know if my connections weren't very good on the first 2 attempts.

Thought it may be ok so put it back in and ran the bike – same problem ECU light with fan on, fan went off with engine off but ignition on.

Performed another test, with the CTS out of the engine I heated it with a lighter and the fan came on with NO ECU LIGHT and engine NOT running (as its supposed to do)

So that’s as far as I have got, any ideas why it works fine out of the engine – could it be an earthing problem, is it earthed when in the engine?

Edited by Mitso

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Just also tried to measure for a elec leak in CTS but seems ok, getting fed up so I have ordered a new CTS nd it its not that will try the earths.

Can anybody tell me where the earthing points are on this bike --much appreciated as I have put in a search and cant find anything.

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Refer to the wiring diagram:

 

CTS is connected at the ECU with a Green/Red wire .  Looking at HARNESS SIDE of the large connector, it is in the seventh position from the right on the lower line of connectors.  By lower, I am referring to the side opposite the lock at the center TOP of the connector.  The common ground line for the 5 volt logic is a Black/blue wire at position eleven lower. According to the wiring diagram, a total of eight sensors use this ground connection.  It's unlikely that the connection at the ECU is at fault, as it would take out all the other sensors also.

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The new thermosensor or CTS arrived today and fitted it - hey presto it works as it should.

What is a little surprising is the fact that the first 2 resistance readings showed an error but the others were a constant decrease as the CTS was heated up. Also the fact that it worked fine when heated with a lighter when not in the engine. So I have come to the conclusion that it is not earthed in situ as all other systems worked fine and apparently share common earths.

I think as BluePill said - it was probably leaking to earth with an internal fault even though I couldn't measure any leak under test.

Thanks to all the replies especially BluePill and hope this will be useful for someone else when they have a similar fault, it was time consuming and irritating but a satisfying outcome. :D

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