Temp warning light

[drajac]

Coolant/temperature warning light on my '06 Jetta TDI is driving me crazy! It randomly goes off blinking, usually with lower temperature and higher humidity weather. I changed coolant reservoir (and checked connectors for rust and coolant migration, all good) thinking it may be a bad coolant level sensor, but issue didn't go away. It was OK for the summer, but as of yesterday, it started again. I checked VCDS (with the light blinking!) and got no fault codes!!! Temperature was showing 87C. I'm thinking it must be a bad connector somewhere or a ghost in the cluster ... Any ideas?

[chittychittybangbang]

Well, at least you know the coolant temp sensor is working. Off the top of my head I seem to recall that the instrument coolant temp runs off somewhere else, could that be bad? I don't have the wiring diagram in front of me so I could be wrong, but it's a possibility since you've already change the coolant reservoir and checked all the plugs. The cluster shouldn't be bad but it's possible. If you need to change the cluster know that you need the SKC off the old and new clusters, see the immo FAQ for more details.

[drajac]

Thanks Chitty. I will look through the wiring diagram. I'm wondering if this sensor has anything to do with ambient temperature sensor. Ususally , it starts failing in high humidity/lower temperature too, and replacement did not help.