UK-POLOS.NET - THE VW Polo Forum

Hello folks,

I bought a Polo 9N (2005 55 reg) earlier this year (Jan 2020). Usage is minimal to rare - about 1000m in the last year at the very most!

The issue is that the temp gauge in the dashboard only works fine the first time you start the car. Subsequently, it stays where it was when you switch off. Then, when you start the car again next time (even after a couple of hours), it starts from the point it was stuck at and creeps up again, going all the way up against the stop pin!

I've changed the temp sensor, flushed the coolant (first with distilled water, then with coolant)... but, the needle still behaves funny.

I'm pretty sure that the engine is NOT overheating... there are no warning lights either.

Question - Is this a MOT failure? Should I explain to the MOT technician before the MOT?

Alternatively... and I suppose this is a more permanent fix... how can I fix the engine/coolant temperature gauge needle in the dashboard?

The temp gauge does not display the true coolant temp between 75c and 107C, once the temp reaches 75C then the gauge will move very rapidly to mid scale which is 90C and will remain exactly there until (or if) the coolant temp reaches/exceeds 107C, if everything is working normally, the gauge will still display 90c even with the coolant fan cutting in/out. This temperature profiling is done either with the instrument cluster control module or the ECU, not sure which but strange that everything is fine from cold. You might just remove the wiring jack from the coolant sensor when next stuck and see if it returns to 50C, also switch off the ignition before it reaches 70C and see if it returns to 50C. A scan may or may not show up a fault. Googling this fault might show some fix from someone who had the same problem.