Thanks. Will putting the sensor in boiling water give me any clue of whats wrong? The wire seems OK.
Sure. You can extend the wire to gain distance off the engine (safety) and introduce the bottom part of the sensor in boiling water. The sensor has to be grounded so you will need two wires. Your temp gage should then measure 100C. If it does not, your sensor is faulty like both mines were. But your test proposal is equivalent to running your engine up to op temp, so I don't see the value added, especially with the effort to extend the wires/boil water, etc. For 10EUR I would go ahead and replace it. As said, it's a pretty sure bet it's faulty. My 2 sensors in 2 different engines were reading 60C when engine was at 100C in reality. I replaced both and problem solved, they now read correctly. I'm pretty sure we are not the only ones here who had that issue. Others can confirm, solution is to replace it especially at that low cost and still available new. Too much of a risk immo to have an overheating engine and not having the gage accuracy to let you know.
Cheers