Hello all, fitted Oxford heated grips to my K100rs 16v last week, started the bike to test the grips were heating, all working good. Took it to work next day, no problem a couple of hours later went to start and ride home and when I turned on the ignition switch, the radiator fan came on and there were no priming noises from the fuel pump. The bike turned over fine and when pushing the starter button, the fan stopped running, when I stopped pushing the starter, the fan came back on. In the blurb supplied in the Oxford kit, it says something about the standard wiring possibly being affected by the heated grip wiring. Anyone else had this problem, or is it just coincidence and a sensor had failed. I've had the water temp sensor fail on this bike and it was replaced about a year ago, so not sure about that. Any suggestions? Thanks in advance, Dave.

Does the bike behave itself if you disconnect the grips? Where are the grips connected to?

What he said - what did you wire them up to?

All K bikes have a factory heated grip connector in the wiring harness under the left rear of the tank.  That's what I always use for aftermarket heated grips.

Hello Dai and Duck, yes, bike was running nicely prior and I followed the Oxford grips wiring diagram, the two grips each have wiring that are plugged into a connector that then goes down to the battery, where it splits, one wire going to +ve one to -ve. I did faintly remember some other discussion about plugging them into the BMW wiring, but didn't consider it. Thanks for the comments, Dave.

Pull ther inline fuse and see if the bike behaves itself again. I suspect the answer is going to be 'no', in which case we look further...

Hi Dai, pulled the inline fuse for the heated grips, radiator fan still came on when turning the ignition key. Have found though that there is a remote switch for the fan hidden underneath the handlebars. The wiring for this goes down to the fan relay in the relay box. I'm going to pull this out and see what this does. Cheers again, Dave.

So, an update. Finally had some time to pull the remote fan switch and associated wiring out of the bike and rewired the grips to plug into the standard BMW heated grip plug. Turned the switch and the fan still comes on. Now, what controls the fan coming on, is it the water temp sensor? Is there another sensor that is turning on the fan, is the relay in the relay box stuffed? All suggestions welcome, cheers, Dave.

The best way to check is to pull the relay, if it stops the fan then that will be the problem. Is it an original relay or a replacement?  I think I read somewhere that the original relays differ in pin layout from normal relays.

bigdavergs wrote: In the blurb supplied in the Oxford kit, it says something about the standard wiring possibly being affected by the heated grip wiring.

If this were happening on my moto, I'd correspond with Oxford to explain to them what's happening, ask them if this is the kind of wiring interference indicated in the blurb, and ask them to explain why it happens.

Stumpy wrote:The best way to check is to pull the relay, if it stops the fan then that will be the problem. Is it an original relay or a replacement?  I think I read somewhere that the original relays differ in pin layout from normal relays.

You're right. Our dear old Ks are fitted with Din-1 standard relays, but yer over-the-counter jobbies are Din-2. The difference is that pin 86 and pin 37 are swapped round. If you get caught on the side of the road the get-out-of-jail free card is to punch out the spade terminals and swap them round.

Thanks for the replies gents, that gives me a couple of things to look at. I did think about messaging Oxford, might do it and see what they say. Thanks again, Dave.

Hi again, finally found some time to try and sort out this problem with fan coming on when the ignition switch is turned on. I pulled the fan relay and fan stopped coming on. Put it back and fan came on. Bought a new, original relay from uk supplier, fitted it, turned on ignition switch, fan came on. Back to square one. Anyone have any other ideas? Thanks in advance, Dave.

Had a quick look at the wiring diagram for the K1100 which is probably close to the 16V K100 and it looks to me that the Motronic unit energises the fan relay by providing a ground.

If that is correct then I would check the harness between the fan relay and the Motronic unit (I don't have the pinouts handy) to see if the Blue/Yellow wire has rubbed through somewhere and is touching the frame thereby energising the fan relay as soon as you turn on the ignition.

Cheers

Maybe this will help a bit;

http://web.archive.org/web/20080405214941/www.geocities.com/fwarner_au/mc_things/K_fuel_injection.html

To test my theory using Arlina's info you would unplug the harness from the Motronic unit and remove the fan relay, then test with an ohm meter between pin 16 on the Motronic plug and the bike frame/ground. If you have continuity (zero or very low ohms) between those two points you have your problem (I believe) and you just have to find where the fault is.

Cheers

Thanks Gaz and Arlina, i'll check out your suggestions and see what happens. Cheers, Dave.

Problem fixed. Thanks for all the advice etc, turned out to be the water temp sensor. Didn't check or think about it because of the symptoms. As they say,"It's never done that before". Had a couple of sensors go on 8v k100s over the years and they just wont start, never had the rad fan coming on as a symptom. Thanks again all, Dave.

Thanks for the update with your results.

  Just today somewhere else I learned that the fan can go nuts with a bad sensor....

Arlina wrote:  Just today somewhere else I learned that the fan can go nuts with a bad sensor....

Replace the bugger.