Hi folk, sorry to ask another question , hopefully eventually I'll be able to post an answer instead, but...

I've read about how hot our bikes can get, and found out for myself recently, in heavy, slow traffic, the fuel tank was so hot, I had to ride with my legs sticking out the fairing (K100LT).

The insulation under the tank is still on, and I'm going to try insulating the fuel pipes.

But it got me wondering why the fan never came on at all. I've disconnected the fan, and powered it straight off the battery, and it works fine.

Trouble is, although I suspect the control box may be faulty, I don't know how to test it. And of course it's pssible that there is no fault, it just hasn't got hot enough to switch the fan on.

Any advice on checking the fan control, or any more tips on keeping things cool would be much appreciated.

Thanks,
Steve

Steve,

The fan should start when the water temperature reaches 103 degrees Celsius.
As a bonus, I give you a simplified schematic of the switching temperature unit. (I just added this one to the download page).



Bert

Thankyou Bert. That's excellent.

Please forgive my pestering, but does that mean if I connect pins 45 and A2 with a piece of wire, the fan should come on, even with a cold engine.

If it does, does that prove the switching unit is faulty?

Also, would bypassing the temperature sensor (join E to prong 10) make the fan come on?

If so, ermm....does that prove the sensor is ok or faulty? I can't get my head round that one

Thanks again.

Steve.

Hi Steve after the bike has cooled down or sat overnight unplug the relay what is the voltage between the socket of pin 45 and earth (with the ignition on that is). Short pin 45 to A2 does the fan run? Then check resistance between the socket of the relay pin Pin E and earth with a good quality digital meter set to measure resistance. Write both down. That will tell you if there is power available to run the fan on pin 45 and if the temperature sensor is around the correct value for a cold engine.

Once you know you have a good value at the relay get the bike thoroughly warmed up and check the resistance of the sensor down at the sensor itself just by unplugging the wire to the sensor and measuring from your previous earth point to the pin of the actual sensor that will tell you if the sensor is changing value when it gets hot, (don't forget to reconnect it).

In the scale of happy results there being no power on pin 45 is probably the best as it is easy to check back via the fuse etc., then a faulty sensor. Lastly a faulty relay as those are a little pricey from memory.
Regards,
K-BIKE

Steve,

Asking questions is not pestering .
You are correct about jumping pins 45 and A2 with a piece of wire. This has to be done at the socket with the temperature unit removed. The fan should start but you won't be able to start the bike as without the unit, pin #9 will not send the signal to pin#87 of the FI relay.
Bypassing the temperature sensor (join E to prong 10) should not be done. I believe that the temperature sensor has 2 different resistors built in: one for the temperature unit and one to feed the FI computer

You may be looking at a problem that may not exist. Are you sure that your temperature was over 103 degrees?
If not, I would first disconnect the temperature sensor and ground the wire going to Prong 'E' of the temperature unit. Your fan should start to turn. The bike may not start as apparently, their is a security to prevent the engine running when the temperature is too high.
Your temperature sensor could be tested too. You will have to empty your cooling circuit to do it.
Remove the sensor and plunge it in a pot of water. Put it on the stove and start to heat the water. Take measurement of the resistance and see if it matches the following graph

Thanks K-BIKE and Bert,

as you say, I may be looking at a problem that does not really exist. I suspect the fan system is faulty, but am not certain. I shall try to get the bike really hot tomorrow to find out for sure.

If I am sure it isn't coming on when it should, I will do the tests you've advised and report back.

Much obliged,
Steve.

Well, I feel such a fool

Checked the voltage at pin 45 =12v
checked resistance at pin E = 2850 (engine cold)

Reconnected wiring, sat fuel tank back on, reconnected fuel pipes.
pushed bike outside, started her up and left her running to warm up ready to re-test resistance.

After about five minutes, yes... you guessed, the fan came on!

Goes to show, always check the simple things before diving in with the spanners.

Thanks for your help gents.

Steve.

It's nothing worse than thinking that something may not work.
At least,now you won't have any fear to ride when it's really hot.
On the bright side, you learned about the cooling system without having to dismantle 1/2 of the bike.

Just as a reminder, NEVER, NEVER aim the gun at the radiator when cleaning the bike with a pressure washer (Karsher). The fan is poorly designed and not waterproof. Water in the fan motor will result in having the plastic brush holders melting.
Once in a while, manually check is the fan blades are freely turning. I know, you need tiny fingers, but just a quick spin is doing the trick.
If the fan becomes a bit stiff, you should remove it and clean it.

Bert

Hi Steve,
You may have had a bad relay pin/socket connection which your work cleaned up. Do the DeoxIT tratment to every plug socket and relay plus the main earths and you will be fairly certain that any problem is not a bad connection.
Regards,
K-BIKE

I am troubleshooting an fan issue as well. If I short pin 45 to A2, the fan does run. If I short 45 to A3, the temp light comes on. So, I thought I had a problem with the Temperature Sensor. It measurs about 3,000 ohms when cold. I shorted the two wires at the temperature sensor thinking this would make the fan come on. It does not. So I figured my Temperature Sensing unit was faulty.

I pulled the Temperature Sensing Unit out and pried the cover off. I can manually close the relay inside it and the fan comes on. So I figured something inside the circuit must be faulty. There is a voltage regulator chip inside there. But it is not getting any power. 0 volts on pin 3 (Vcc) So without any power getting to that chip, nothing in that circuit board is going to work. So I orded a used one off of Ebay. And tonight, I plugged it in, shorted the wires at the temperature sensor and still, the fan does not come on.

Hopefully, I am missing something here. Any thoughts would be much appreciated. Oh, and by the way, the highlighted electrical diagrams on here are great. I really appreciate the work put into it to create them and post them for us all to use.

Eric

Just a quick thought the temperature sensor on some models has two resistors inside I am being sent to do a job by SWMBO. If you have a dual resistor sensor each pin is grounded to the case of the engine then shorting them together I don't think is going to make the fan run.

Take a close look at the circuit board, these electronic circuit relays are known to develop cold solder joints (fatigue cracking really). That can stop them from working so check and reflow the solder on any suspect joins.
Suggest you check your specific year to see if it has the dual resistor sensor.
Regards,
K-BIKE

You're right. With the two pin temp probe one gives a signal to the temp relais, the other goes to the ECU (pin 10). Shortening between them two won't achieve anything.

With the new temperature switch in, I shorted both leads of the temperature sensor to ground. Still no fan. I can't figure this one out. So I am going to put in a temperature gauge and a manual switch in the next couple fo weeks. The manual switch might help keep the bike cooler in the heat of the Texas summers anyway.

Hi Justride,
Do you know your used ebay relay is working? I ask because you had a suspected faulty one, you replaced it with a second hand one.
Have you confirmed the relay has a good ground connection? See Bert's diagram above, all of the tests you have done do not rely upon the relay to have a good earth connection and even with a perfect relay having no earth connection on the relay will disable it.

Could I suggest you probe with a test light between pin 15 and the relay earth if the bulb lights you have earth there. Are you sure the other connections to the relay base are intact?
Regards,
K-BIKE

I noticed a "typo" on my schematic of the temperature switching unit.
Pin #45 is in fact pin#15. The schematic is OK, the mistake is just on the numbering of the pin.
Sorry about that.

I am working on marking all pin #s on every diagrams. It should be done soon.

Bert