Hi, I am trying to fit an aftermarket Digital Instrument cluster and have a question about the Temp Sensor setup.
The device a Trailtech Vapour Stealth seems to have a RTD style input which relies on resistance change to display temp change. On my initial searches I have found a Violet/Black stripe wire but am pretty sure this is just a switched output?.
Can anyone inform me if my assumption on the Violet/Black Stripe wire is in fact a output that becomes active at a set temp value, and if so what is the temp that the light comes on at.
Also is there a RTD fitted on the BMW K100?. I will keep searching the net but thought I would post this for some hopefully quick assistance.

Thanks

Making some headway thanks to the Forum. think I have determined that there is in fact an RTD located near the water pump. Now just need to confirm and then try to work out resistance values to allow calibration to new meter. Measured resistance of sensor supplied with new gauge at ambient and have confirmed resistance drop with heat applied. just need to confirm what the factory resistance values are.

Keg wrote:Making some headway thanks to the Forum. think I have determined that there is in fact an RTD located near the water pump. Now just need to confirm and then try to work out resistance values to allow calibration to new meter. Measured resistance of sensor supplied with new gauge at ambient and have confirmed resistance drop with heat applied. just need to confirm what the factory resistance values are.

The RTD (resistance temperature detectors) is a dual one.
One side is used to feed information the the fuel injection system, and the other one is to activate the fan.
Here is the values for the EFI side:

the temp sensor used in the efi management and fan control ...is a true indication of the heat leaving the engine ....and mounted in the water stub behind the radiator

the additional sensors , usually used for temp indication are mounted in the water pump area ...are ntc ..(negative temperature co-efficient ) and serve well to give an indication if things are running correctly(ie that the cooling system is running correctly ) . most of us are well used to seeing this on the usual temp gauges fitted to the "k"
and I suggest you look into this
the range of resistance of the factory units (sensors )  is not a commonly found value ...these days 
you will find that the sensor is a 12mm type x 1.5 pitch from memory  

if you have the sensor that came with the instruments and its 12mm I would be installing it down at the water pump and then wire to the acewell as expected .....you may find that the current common sensors will mate up with the acewell correctly

Thankyou all for your feedback. I have confirmed that the Trailtech does have a 12mm x 1.5 RTD sensor available with a 900mm lead. My only concern is that if I install that I will affect or remove the signal to the Fuel Injection system. Thinking for the short term I may be better off utilising the Violet with Black stripe wire and just running a warning light, and to leave the factory RTD and control circuit as is.

the sensor at the pump is ancillary to the motor operation and is self standing indication only,  in no way is it or does it affect the running of the machine

put the sensor in ...and be glad you have additional feedback to the good running of the motor and cooling system .
sorry for getting the gauge system name wrong ..

Charlie99  I am sorry I did not read your post thoroughly before my reply. I really appreciate your and others assistance in this and other matters.

I have finally read your post earlier today, and since ordered a temp sensor and adaptor and will proceed to install the Trailtech vapour sensor unit. Which as you say will give real time read out as opposed to a warning light when things have already gone bad.

Once again kudos to the forum, absolute priceless source of information which enhances the K100 ownership experience.