ok after the old girl being off the road for so longi did a few 1 of was clean out the fan and grease it . cos it wasent working i then bench tested to make sure it would spin, i have ran the bike for about 30 to 45 mins till i could feel bubles in the hoses, but no temp light and no fan, any ideas thanks
alex

Grounding issues for the temperature sensor are a known problem for the K100RS. Check all the wiring associated with the sensor. The sensor is at the right front, behind the fairing, near the radiator.

When I got my RS running, I just let it sit, running at idle in the driveway. The cooling fan came on after about... well, I didn't time it.

This would be a good FAQ item for this forum: Start a K100 from dead cold, and let it idle. How long, in minutes, until the cooling fan should turn on? Five minutes? I know mine did in less than 10, but I wasn't timing it. Anybody else jump in and help?

The first step is to check if the fuses #6 and #7 are good. Then check if the temperature sensor and the fan are working.
The sensor has 2 outputs: 1 for the EFI and one for the temperature unit.
First check that the there is continuity on the wire between the water temp sensor and pin E of the temperature unit.
Check for continuity between the fan and pin A2 of the temperature unit. If its OK, remove the temperature unit and power the connector for pin A2. The fan should start spinning.
If the fan is working, check the water temp sensor. You can remove it, and test it in a pot of water that you slowly heat up. Check the resistance for each increase of 10 degrees. At 103 degrees (Celsius), the resistance should be very low (between 0 and 250 Ohms).
Below is a chart of the ratio resistance/temperature for the sensor.



If the sensor and the fan are OK, ground pin E of the temperature unit and see if there is power at pin A2. If you don't get power, you certainly have a bad temperature unit.


Bert

BadjerJim wrote:This would be a good FAQ item for this forum: Start a K100 from dead cold, and let it idle. How long, in minutes, until the cooling fan should turn on? Five minutes? I know mine did in less than 10, but I wasn't timing it.

It takes about 10 minutes for my fan to come on. This is with the bike running at high idle (1,500 rpm). Once in a while, I let the bike heat up to check if the fan is working. I also heat the engine this way before changing my oil. I then let the oil drain overnight.

On my bike, I installed an LED on the fan circuit. This way I can see when riding if the fan is running.
At around 5,000 rpm, the led starts to glow . I don't know why. It may be the fan spinning on its own because of the speed and air pressure and it acts as a generator. Anybody has an idea?

hi thanks guys i have checked all my fuses there all good, guess i will have to get stuck in to it with a multi meter in the next couple of days, the front right, hmm i thought it was at the front left ontop of the motor behind the fuel rail, access it from the left side tho. and the sensor on the water/oil pump is that temp or oil pressure..
thanks for ur helpfull sugestions

The sensor on the oil/water pump is the oil pressure sensor
Here is the exact location of the water temperature sensor:

Mr. Crazy Frog: this is GREAT stuff. THANK YOU for your time and input. I'm blown away. Thank you!

You're welcome. Let us know what you find.

Bert

Bert,
Could I run a switch tapping in from the temp sensor to my handlebar to have manual control (ie; in traffic) and if yes would it interfere with other electronics?
Ajays

ok thank that b the devil then... photo threw a vent in the right faring

Ajays wrote:Bert,
Could I run a switch tapping in from the temp sensor to my handlebar to have manual control (ie; in traffic) and if yes would it interfere with other electronics?
Ajays

This is very easy to do. You just have to short the side of the temperature sensor going to the temperature unit. I would be safe to have an LED or bulb letting you know when you bypass the sensor.

ALEX PITON wrote:
ok thank that b the devil then... photo threw a vent in the right faring

The plug is not easy to remove. There is a wire clip around. You have to get a very small screw driver and slide it under the wire. You then spread the clip apart. This is the same type of clips that you find on the injectors or the idle switch. Better to try removing the clip on the idle switch to see how it works. At least it's accessible. The temperature sensor is difficult to access and if you haven't seen these clips you could work for hours before taking it off.

Bert

Thanks Bert,
I will be doing that as soon as the weather warms up a bit.
Ajays

ok 1 more qick question dose the temp light prove, before u start the motor.... i see oil press, charge and choke light up befor start.

The light temperature is working only when the engine overheat. It's not going on when you power the bike. This would be good to test the bulb, but the way the wiring is done, the temp sensor has to be over 100 degrees to trigger the temp unit.

ok got some news, not exactly sure yet as i belive i am left with 2 possable answers, 1 a broken wire to the fan or possably the realy,
am unsure be cause i am useing a jump wire and a headlight bulb with wires attached... could not check continuity in the wires untill i get my hands on a multi meter, but, suppling power to A2 : fan didnot start, the test headlight didnt light either at the connector for the fan, so i guess no power, the temp light lit up tho... .
when i grounded E, there was verry little or no power at A2 this was done with relay both in and out,

If when you put power on to A2 the fan does not run that argues the wire, fan or earth from the fan are faulty.
Regards,
K-BIKE

I agree with K-Bike.
If you disconnect the fan and put power on the 2 leads of the fan, does it turn?

Don't give up. This is the best way to learn electricity.Just think about water pressure. The positive being the pressure coming from the pump (battery in electrical circuit) and the negative being the drain going to the sewer.
If the drain is plugged, you will get an overflow. If the pressure side (tap or positive in electrical) is plugged or restricted nothing works. If you have a corroded ground, it's like having a plugged drain . If you have corroded connection on the positive, it's like having the tap spout half plugged. The flow will decrease and the pressure will increase.
If you have a leak and the pressure goes straight to the drain, the electrical equivalent would be a short.
All of this can be translated to voltage(flow) and amperage(pressure).
Now, to put that in perspective, is the hose going from the temperature unit to the fan free? does it has a cut or a kink that would reduce the flow and increase the pressure? Did somebody cut the hose and put a plug on it or somebody cut the hose and put it straight in the drain (short)?
I know, it's very simplistic explanation, but it's the best way that I can explain the flow of electrons. Nothing more than a fluid.

voltage(flow) and amperage(pressure).

Sorry Crazy Frog, voltage = pressure, amperage = flow.

Not saying this is the issue that Alex faces but a problem we all face with our bikes (unless we are the original owners) is that previous owner(s) may have made "improvements" in the bike or just plain disconnected things they felt they did not need or caused them a problem.

There is also the problem that owners of ex Police bikes may find some very dodgy wiring disconnections after the Police mechanics ripped out the radios, sirens, lights, and any other specials they had installed.
Regards,
K-BIKE

i dont think it is a earth wire causing the problem , because if u run a wire to a headlight bulb from b+ and then from the bulb to the negative of the fan circut the bulb light up really well, so i belive that tells me there is a good earth there... as for the fan spinning i have not had a chance to look again yet, had rwc issues with the bike, i should have it all sorted now thow, so it just the fan now working and a flat spot, and when i get adventerious look a the chutch bobbin and alti drive, to try and get rid of that niose

Let us know how you go.
Regards,
K-BIKE

I looked at mine this morning, fan not working. Went thru the system and the fault is either faulty temp sender or corroded connection on sender, (most likely corrosion)
So decided that rather remove half the fairing and battle for hours getting the plug off, I spliced into the wire off the sender as above and fitted an accessory switch up on the handlebar pad. What I found is when I turn the switch on, the fan works as expected, but as a bonus the temp light comes on, a easy way to remind me that the fan is on, saves having to wire in a led or something. I just hope that it doesn't actually get hot enough to turn the light on as I would not know. I really hardy need the fan to work anyway, all my riding is open road, never trickle around in heavy slow traffic, and down here in NZ we do not get the extreme hot days, rarely gets over about 28 degrees C around here. the only time I would ever use the fan is if I did end up in a city crawl. Next time I have the bike in bits I will look closer at the temp sender. Also discovered while checking the fan fuse, I originally thought I had a problem there as I had no power on either side of the fuse. This fuse also covers the fuel pump and has no power going to it until the motor is running.

Well at least you know the temperature light actually works and might be worth the effort of fitting a temperature guage rather than relying on a globe.

I have found with mine even 30kmh on a warm day is enough for the fan to cut in and out but I think the RS fairing is a little kinder to the engine than the RT.

Regards,

Phil

robinm wrote:
So decided that rather remove half the fairing and battle for hours getting the plug off, I spliced into the wire off the sender as above and fitted an accessory switch up on the handlebar pad. ....... I just hope that it doesn't actually get hot enough to turn the light on as I would not know.

Robinm,

What you did is to bypass the sender. What you should have done was to install your switch as an override.
With the solution that I propose on the following circuit, your sender is still 100% functional, but if needed when switching your override (in blue) your sending the ground to pin E of the temperature unit and the fan will start.
It should be very easy to modify your splicing to switch it to a override one.


WARNING: Only install a bypass or override on the proper lead of the sensor. If you install it on the side feeding the FI unit, your engine will run like crap. Water temperature is one of the parameter used to determine how much fuel your engine requires.
As we talk in another post, installing a bypass on the FI side of the sensor could be use as a bike immobilizer. If the engine is too hot, it will NOT start (but if its running, it will continue to run as long as you don't shut it off). By shorting the sender, you signal to the FI unit that the engine is in an overheated state.




Now that you have the wires coming to the handlebar pad, it is easy to check if the temperature sensor is working or not.
In stead of the switch, install your ohmmeter and see if the resistance decreases as the engine warms up. Here are the values of the resistance vs temperature:

That is exactly how I have wired the switch, just as your diagram.

Some people bypass the sensor and apply the ground with the switch.
The way that you wired is the safest way and if you replace you temperature sensor, you will have a regular circuit + the opportunity to override it.

Good thinking, good job.

fitting a guage . that is an idea i have had, if ne one has done it let me know and how they done it would be nice thanks, my idea is do drill a hole into the knee boards and fitt a 2 or 3 inch guage into the top, also wanted an amp and oil pressure,, read some thing on here about a dash but i thinks it is behind the speedo .and mine dont have, think it was on a newer model, also anther thing i seen on ebay the other day a radio n speakers for an rt, where was that fitted and can i do it to my rs ??

oh ps bike failed rwc on the rear wheel barings i did, i buggered up the shims 40 thou out i was but fixed now and back on the old girl,
bit of a bad hesitation still on take off

Hi Alex,

I am pretty sure the K1's have the gauges in the kneeboards so might not be a bad option and I think the radio option is RT/LT only as it is designed to fit in the lh pocket.
Might be easier to get an iPod like device with an AM/FM tuner, as the RS is not quite as roomy as the RT.

Regards,

Phil

The RS has two inserts one each side of the fairing panel and above the knee boards where the additional gauges are meant to be fitted, I think yours should be the same. Usually people fit a fuel gauge and a temperature gauge. You could fit an ammeter but vibration is the problem with the needle thrashing about. I would opt for a smart voltage monitoring LED circuit as I described in a much earlier post since as long as it is OK the value of current flow is not too important.
Regards,
K-BIKE

ok cool thanks for that i might see if i can get the k1 guages then ... thanks

When I take my inserts above the knee boards out they are helpfully marked with the circles for the gauges and the metal behind will take them through the back.
Regards,
K-BIKE

thanks i havent even looked yet, but will take note as soon as i do

I have a switch fitted in the 'crashpad' below the speedo which connects E above with ground and thus functions as a manual fan switch. A possitive of this is that then the high temp light comes on as well, showing it works (and reminds you that the fan is still on) as posted earlier.

The temp sensor is easy to measure between pins 10 and 13 of the ECU connector and between E and ground. These are two seperate circuits. If you end up having to renew the sensor make sure you check/clean the ground path of the sensor. This is through the little stub and the bolts, where it connects to the block and the sensor thread inside the stub. Best done after removing the radiator.

I have fitted a volt and coolingwater temp gauge as well in the left hand pocket. I have speakers in the fairing part where otherwise the gauges could have gone. I intend to fit an oil pressure gauge as well, but that's next winter's project.

Hi
I fitted a switch today to turn my fan on, i want to use the earth as in the image to E, i turn the ignition on, with the relay in i used a piece of wire and jumped from E to earth, but the fan dont run, if i jump from 45 to A2, without relay in, the fan will start and if i earth to A3 the temp light comes on.

Is my relay faulty? is this why it may of overheated on me?

the only thing i have not got on is the tank, everything else is connected as should be.

It really looks like your temperature switching unit is bad.

Sorry for the bad news :pale:

Thanks, just needed to check that it should have worked. Have sent a message to a member whos splitting a k100 on here, so hopefully he will do a good price

theres one on ebay for £12.95 might be best to get this?

Pity you don't live a bit closer by, you could have borrowed my spare to test. Then again if you sent me a PB with address etc I can sent you one to check, then you know for sure.

That's very nice of you Rene!

thanks for that renez must appreciated.

Crazy Frog wrote:...
At around 5,000 rpm, the led starts to glow . I don't know why. It may be the fan spinning on its own because of the speed and air pressure and it acts as a generator. Anybody has an idea?

yes is true

I tested it in my old car
Fan works then as generator....

you can put diode on wire do led stop this effect

I have a question...

did BMW K100RS have sensor to mesure temp. of coolant or switch to turn on the fan?

I want to build small onboard computer.

All K engines have a temperature sensor. It feeds the electronic injection as well as the temperature switching unit (Relay for the fan and the temp light)
I would be very cautious about installing something on this circuit as it can modify the parameters sent to the FI computer.

yes you're right it might be not good for parameters reading

What do you want to do? It might have been done before.

I want to do a small onboard computer (procesor and LCD display). It allows me to read and control the temp. off coolant, oil, air and voltage, control

OK, no worries. The sensors come with some basic info. If you want to get it right you will need to map them.
Difficulty is that you need to make sure that, if you take your info from existing sensors, you don't interfere with the signals going to the ICU and ECU. You can do measuring, I think there's little you can do to control. But that's me.

LifeGuard wrote:I want to do a small onboard computer (procesor and LCD display). It allows me to read and control the temp. off coolant, oil, air and voltage, control

I know exactly what you want to do. I often like to have all the values readout on a single display mounted near the instrument panel. Don't forget to add oil pressure and temperature.

I think that the simplest thing is to get a "piggy back" plug to your ECU and use that to tap into the signals. I suspect that all you need to do from that point on is make sense of voltage signals.

BMW and others have things like that ... you can even get them on e-bay cheaply, but, i know, that this is not as much fun as building one. look for a diagnistic electronic tools ... I forget the actual name.

BTW is your bike L-jetronic or monotronic ?

My bike is K100RS '87 it is L-jetronic