Temp needle jumping .

On some Passats there is a sensor at the rad which is a dual thermal switch to activate the fan and another coolant temp sensor which is in the back of the engine head, up top.The one in the head would be the one needing changing , assuming you changed the correct one I would check wiring to sensor .

I did change the coolant sensor genuine from vw green one .

Since that happen the temp needle it use to be right on the middle now it's a bit over .

Normally sensors have a operating temp stamped on which I always check and verify is the same as the one removed before fitting .

I disconnect it the plug from coolant sensor it did the same thing .

Hi and also 1 month ago passenger side was flooded underneath the carpet ,that's when that problem start it with temperature needle playing up .

Hi I got passat. 03 1,9 tdi pd engine I would like to do remapping on it but I am not sure if it will damage the engine ,I would like to get same opinion .