Water temp reading

[jonesya3]

Have a problem with the water temp gauge on the dash, 95% of the time its fine but sometimes it seems to stick at 0 then shoot straight up to full temperature after a long period of driving, any idea's on what going to be the most likely cause of the problem temp sensor or thermostat ?

scanned it with vagcom not fault codes found, also any rough prices on the above 2 parts cheers

 

[cus]

mine does this. but only in the winter months... haven't bothered replacing anything, as i'm going to see if it gets better when the weather gets warmer

 

[chumsofmanutd]

Sounds like an issue with the coolant temperature sensor