K Series Temperature sensor for mini dash

[Mini Vvc]

Hi all, What sensor is everyone running on their K series engines for the dash temperature readout. I have the original 2 clock dash and when connected to the original vvc brown sensor or blue sensor it just goes right up to hot.

Is it best to get an original single wire mini sensor and make it fit?

All info much appreciated. Thanks

[AGoaty]

The sensors are basically a variable resistor. The K series and A series engines use a totally different range on them, hence the gauge going straight to the top. Two ways you can resolve this, first, use the A series sensor or fit a resistor in the line for the gauge. Neither way is easy as the A series sensor is likely the wrong thread for the K series elbow. Fitting a resistor is going to be a guess at the value in ohms. I did the same idea for the fuel gauge though, connecting the MPi sender to Rover 200 clocks. I got it very accurate trying a few variations. Try buying a set of ceramic resistors of values around 50, 75 or 100 ohms. Fit these in line or in parallel and work out what works for you. A pack isn't even a fiver so worth a try...

Andrew.

[Mini Vvc]

Thanks Andrew, that's some good ideas. I've bought a mini sensor to try. I hadn't thought about the resistor idea. If it seems too hard to get the mini one to fit then I can use the mini one as a guide to where the readings should be. Eg put the mini one in boiling water to find where the guage sits then use the rover one with different resisters in boiling water to find the correct one.

Thankfully I'm using the original fuel tank so can use the original tank sensor.

Thanks for the tips 👍😃

[Coaster]

If you are willing to experiment with boilin water, you could try connecting a multimetr set to ohms and check the resistance at your desired temp and then add resistors to get the desired value. If you havent played with resistors before, they usually come with coloured rings on the body that denote the resistance. The firtst 3 give the value and the 4th( usually gold or silver) gives the tollerance (silver 10%, gold 5%) the coloured rings tell you the resistance in Hundreds - Tens - Units, look for resistore colour code on Google. Also as Andy says, resistors connected in series add but resistors connected in parrallel divide.

[Mini Vvc]

Thanks Coaster,
I've used resistors before but it's been a while. I'll definitely try out your advice. Much appreciated. Whatever I do I'll post it on my build blog for everyone to see. 👍😃

[250ptm]

Here's how i did mine. the gauge is accurate to 5C

link: cel issue? - 16v Mini Club Forums see post 59

[Mini Vvc]

Thanks 250ptm. That's a good write up on how to select the correct size resistor. I think I will be following that method. Thanks 👍

[Mini Vvc]

Well I carried out the experiment as posted above and thought I would share my results for others to use. I was comparing the standard A Series sensor to the Rover K Series Sensor. I used a digital thermometer to keep track of the rising temperature and wrote down the resistance of each sensor at given temperatures. See the picture for the setup which I then ran on the hob up to 100 degrees C.

IMG20211004220049 by Tim Wells, on Flickr

[Mini Vvc]

IMG20211023031149 by Tim Wells, on Flickr

Here are how the results came out. The sensors were pretty similar at the beginning of the range and at the end. Between 65 C and 85 C there was a maximum of 17% difference between the sensors. I think that they are similar enough to use without adding in any other resistors as at high temperatures they were very similar. This is the area of the sensor that I want to be similar as I want to know if the engine is over heating.

I also did a test with the 2 sensors in a pan of hot water that I carried to the garage and connected to the car. They both showed a very similar reading on the original Smiths clocks. So if they are the clocks you are using too then they should work fine. The pointer is pointing almost directly in the middle on the picture.

IMG20211006063128 by Tim Wells, on Flickr