Lots of bikes use the KTY-84 sensors, and that is probably because they are rated for very high temperatures. Your typical NTC 10K thermistors are rated for -55 to 125C. We know ebikes can easily go above 125C. A real KTY 84 will work up to 300C.
The KTY-84 sensors have been discontinued. But you will notice that they are for sale cheap on ebay and aliexpress. These are all knock offs.
Here is what I found in my testing.
the KTY-84 knock offs will actually read the correct temperatures up to 1400 ohms, or up to 155C. As soon as these go above 155C or 1400 ohms they actually start to quickly fall in ohms. This could be an issue because if you spike the temps quickly above 155C, the temp probe will start to drop from 1400 ohms towards 1000 ohms. You could easily be at 180C and think you are only at 120C.
The knock offs also don't have polarity and are not marked with a black line. They work the same way no matter which way you hook them up.
A Real KTY-84 temp sensor will work up to 2600 ohms or 300C.
These will have to be hooked up with the correct polarity. If you hook it up backwards they will climb in ohms to 1500 or 180C and then quickly start dropping.
If you hook them up correctly they will climb all the way to 2600 ohms.
Does any of this really matter? well, if you really never get your temps anywhere close to 155C maybe not. I do call into question how reliable the temp readings are with the knock offs. While they do report the correct temps at room temperatures, I'm not going to waste my time testing if they actually work correctly up to 150c.
If you are installing a KTY-84 temp sensor you can find them for sale from very few ebay sellers, and they usually will cost about $10 compared to $1.00. You have to be very careful what you buy and ask for pictures and resistances, because you may not get a KTY-84/130 but a KTY84/150.
Picture below is fake or knock off KTY-84 on the left and real KTY-84 on the right. Notice no black circle on the fake, which usually designates polarity.
This is how I quickly test these with a heat gun and volt meter.
The KTY-84 sensors have been discontinued. But you will notice that they are for sale cheap on ebay and aliexpress. These are all knock offs.
Here is what I found in my testing.
the KTY-84 knock offs will actually read the correct temperatures up to 1400 ohms, or up to 155C. As soon as these go above 155C or 1400 ohms they actually start to quickly fall in ohms. This could be an issue because if you spike the temps quickly above 155C, the temp probe will start to drop from 1400 ohms towards 1000 ohms. You could easily be at 180C and think you are only at 120C.
The knock offs also don't have polarity and are not marked with a black line. They work the same way no matter which way you hook them up.
A Real KTY-84 temp sensor will work up to 2600 ohms or 300C.
These will have to be hooked up with the correct polarity. If you hook it up backwards they will climb in ohms to 1500 or 180C and then quickly start dropping.
If you hook them up correctly they will climb all the way to 2600 ohms.
Does any of this really matter? well, if you really never get your temps anywhere close to 155C maybe not. I do call into question how reliable the temp readings are with the knock offs. While they do report the correct temps at room temperatures, I'm not going to waste my time testing if they actually work correctly up to 150c.
If you are installing a KTY-84 temp sensor you can find them for sale from very few ebay sellers, and they usually will cost about $10 compared to $1.00. You have to be very careful what you buy and ask for pictures and resistances, because you may not get a KTY-84/130 but a KTY84/150.
Picture below is fake or knock off KTY-84 on the left and real KTY-84 on the right. Notice no black circle on the fake, which usually designates polarity.
This is how I quickly test these with a heat gun and volt meter.
