Hi Andy
It seems to me that you may have 2 separate problems. The temp sensor has 2 sensors in one unit, one for the fan and one for the ECU/temp light.
Have you got a good circuit diagram and manual? If you need them PM me and I can supply them.
Check that the sensor has a good earth to the water riser as each of the 2 sensors work to earth and we have seen a couple that have had an earth problem and were fixed by a good clean. Have you got the correct sensor the K1100 16v looks almost the same but only has one sensor in the housing.
The fan will turn on at 103°C and the light comes on at 111°C so just because the fan comes on doesn't mean the light will come on

RicK G wrote:Hi Andy
The temp sensor has 2 sensors in one unit, one for the fan and one for the ECU/temp light.

Have you been smoking something illegal again Rick?
It's one sensor to the ECU, the other to the relay that manages the fan and warning lamp.
Just check the wiring diagram.

Andy S wrote:

Fan spins by connecting A2 to E

Overheat light NEVER COMES ON, no matter what the temp is

Taking some hints from the forum and since none of the above worked;  connected E, (in the female connector  temp relay) to the battery +ve. Put a manual switch to make fan go.

Inserted the relay on top of the connector and put everything together.               

The problem must be in either the sensor or the relay, to check the sensor......
measure the resistance to ground both at the relay socket (E) and in the ECU contact (10)
the values should be equal or very close to.

What doesn't quite make sense is that the fan starts when connecting the sensor (E)
and the fan 12V+ supply wire (A2) together.
And then the sensor (E) and 12V+ together.
Are you shure you haven't mixed the designations?

The fan should start when bridging A2 and 15, or A2 and 9 in the relay socket.

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Rick many thanks.

Following is my response:

>>Yes, I have a circuit diagram, thanks. Will try to trace wires if you walk me thru it.

>>It’s a 8V K100LT 1988- VIN 05060516

>>Temperature sensor 61311459197

Got it by part / VIN number from BMW AG, so it should be the right one.

>>cleaned the contact surface b/w the sensor and the engine housing thoroughly at installation.

>>cleaned the grounding of the 6 earth lugs on the frame left main tube

>>I don’t know the temps actually, but while checking if the fan came on, I waited for it to be warm enough for the expansion tank to mildly start spewing coolant.

>> INGE san, thanks for your help.
This is the spade ive connect to battery. Pls comment.



Questions

>>Ive given power to the E (purple/yellow) pin on the female directly from battery with a switch. Is that ok, or …?
BTW, the fan will come on even if the bike is off.
Asking because, as long as she runs ok, I don’t have a problem with a switch.

>>In order for the switch to work in a case like mine, does the relay have to removed or does it stay on?  I have kept it jacked in.

Andy S wrote:>>Ive given power to the E (purple/yellow) pin on the female directly from battery with a switch. Is that ok, or …?

The E terminal is the connection to the sensor, and you would possibly fry the
relay by connect this to 12V+.
But you could connect this to ground to test if the relay functions properly,
then the fan should start and the warning lamp show.

The wire you have put in the relay socket on the picture is connected to
terminal A2 which is the output from the relay to the fan motor, this
connection is OK to use via a switch.

Andy S wrote:
>>Yes, I have a circuit diagram, thanks. Will try to trace wires if you walk me thru it.

Have you seen this diagram?
Just click on the "fan/temperature" tab and you will see the whole circuit for the fan.

CF

Thank all for your support.

i shall make the switch permanant knowing that its safe to use and not interfereing in any other function except the fan.

now posting the hesitant engine in a seperate post.

Cheers!

Could be a better idea to find why your fan doesn't start in the first place in my opinion.

If it functions as it should you don't have to monitor the temp all the time,
the switch you still can have beside if you want the fan to start earlier.

It's described earlier in this thread how to test the sensor and relay.

yes, will do exactly that!

many thanks!!

Since i have the attention of all you K100 gurus, another small question pls.

this jack has been dangling near the water bottle ever since i got the bike some yrs ago.

can anyone tell me what it leads too etc. on a circuit diagram?

i can not locate male of this anywhere in that neighbourhood.
thanks in advance

It is for interrogation and reset of the ABS system.

Put a small manual switch to put the fan on/off as i please.
Powered the y/p female under the temp sensor relay and closed it up.

Not perfect, but works for me.

Couldnt have done it without you gents help!

Inge K. wrote:

Andy S wrote:>>Ive given power to the E (purple/yellow) pin on the female directly from battery with a switch. Is that ok, or …?

The E terminal is the connection to the sensor, and you would possibly fry the
relay by connect this to 12V+.
But you could connect this to ground to test if the relay functions properly,
then the fan should start and the warning lamp show.

The wire you have put in the relay socket on the picture is connected to
terminal A2 which is the output from the relay to the fan motor, this
connection is OK to use via a switch.

This article was very interetsing as I am trying to test the fan on my K100RS. Unfortunately the relays on my bike are not the same as in the above article. The only diagram I can find that represents what I keep under my tank is as below.

Can anyone tell me which terminal to earth (presumably on the FAN RELAY) to see if the warning light and fan come on. The light currently works but the fan does not.

I have stripped down the side panels and front trim to try to find some way to connect the fan with a battery but it appears that I will need to remove the radiator to do that, in which case I might just as well get a new fan whilst I am at it. I would like to test the relay first though.

Many thanks


 

First give the fan a flick to see if it spins freely, if it's stiff, the fan could be further damaged by supplying power to it. 

As Inge says earth to pin E should get the fan to spin, as well it would test the whole system, but in your case, since the temperature light works, the earth signal is possibly good. With the ignition on and a jumper wire between A2 and 15, the fan should work (15 is power from the fuse for the fan, and A2 is power to the fan from the relay)

Another thing to try would be to unplug the fan (the plug is close to the fan) and connect a battery to it, if it doesn't spin, the fan is the problem.

daveyson wrote:As Inge says earth to pin E should get the fan to spin, as well it would test the whole system, but in your case, since the temperature light works, the earth signal is possibly good. With the ignition on and a jumper wire between A2 and 15, the fan should work (15 is power from the fuse for the fan, and A2 is power to the fan from the relay)

His moto doesn't have those connections because it has a Motronic system.

If this were my motp terminal, 85 would be my choice as the ground connection for the fan relay. The fan relay doesn't trigger the light; it just operates the fan.

Yar I got lazy, should have read the whole thread and found the year of Zara's k100. 

I would have been better to refer to the wire colours rather than numbers. So a jumper wire from green/brown to violet/yellow should get the fan on her brick to go, I'm thinking now (if it's the relay that's the problem)

daveyson wrote:Yar I got lazy, should have read the whole thread and found the year of Zara's k100. 

I would have been better to refer to the wire colours rather than numbers. So a jumper wire from green/brown to violet/yellow should get the fan on her brick to go, I'm thinking now (if it's the relay that's the problem)

Thank you Daveyson and Laitch. I eventually found the connector - I was looking behind the fan when it is in the space below the tank amongst loads of other cables. Once found, I quickly worked out that it is the fan that is not working - I have tried both jumper leads and using my multimeter. Zilch in both cases but the fan does rotate easily. I may try removing and cleaning up the fan before looking for a new one. The bike sat unused for many years before i bought it as a retirement project and I have already had to strip and clean the starter motor as the terminals were dirty/corroded - maybe the same has happened to the fan motor. I bougt it as a 30 year old bike with 19K miles on the clock - receipts, MOT's service record all indicate a genuine milage. It keeps me out of mischief and learning new skills.

The OEM fan motors are a known source of problems. There demise can be slowed by fitting an over ride switch and exercising them occasionally, they seize from lack of use. There are substitute fans available a popular one being a Spal. I have fitted a Davies Craig Australian manufactured fan with an over ride and it hasn't missed a beat in over 20 years.
Regards Martin.

Yah, wishful thinking I know, but I'm gunna hope for a bad wire between the plug and the fan, or something silly like that.

daveyson wrote:Yah, wishful thinking I know, but I'm gunna hope for a bad wire between the plug and the fan, or something silly like that.

Thank you Daveyson for your positive thoughts but when I had the fan removed and on the bench, it was very clear that one of the brush mounts had snapped off completely. Hopefully a new SPAL unit will soon be on it's way from Germany. Unfortunately since Brexit, most items coming from UK have 50% taxes etc added so I am now hunting around for reliable suppliers in EU. C'est la vie.

For a good EU supplier check out www.tills.de

Tills.de is really good.

Would anyone know the specs on that fan from Tills? I see that it has 7 blades like the OEM but what is the RPM? I emailed Tills.de but they are out of office until June 22nd. RPM of the OEM fan is 4,500.

RPM is meaningless.  You want to know what the airflow in cfm is.  I think the stock fan is somet hing like 350 cfm.

I bought a fan from Tills.de fairly recently at a good enough price. I got it to have for my 83 RS as I feel the original fan will fail at some point. My intention is to replace it if I am in there for any particular reason doing other things. I would just go ahead and buy one.