Mk4 coolant temp/level dash light...

[squabeggs]

Comes on and blinks... on the first start up on really cold mornings. After a minute or so it goes off stays off for the rest of the day....unless it sits for a very long time out in the cold. Only have this happen on really cold days.
Fluid levels are good and indicated temp is stable and fine once warmed up (190º).

I do not have a "green top" sensor, and I am thinking that this old black one just needs replaced.

No CEL or any other abnormalities.

Thoughts?

[Mikewire]

The coolant light on your dash is telling you that coolant level is low. The green/black top sensor in the motor tells the ECU what your coolant temp is.

So, knowing that you have the dash light you may want to double check the coolant reservoir level. I know you said it's OK, but G12 expands and contracts more than green coolant, so check it cold, and make sure it is sitting at or above the MIN mark. Then check it HOT and see where it is sitting, and top off if needed.

If you used all/only distilled water when filling the reservoir, a tip is to give it a splash of tap water. Apparently the minerals etc. in the tap water helps the coolant level sensor get the correct reading.

My Jetta used to do this in the winter as well, then I found out that the coolant flange was leaking, so take a look. I have a coolant flange DIY in the DIY forum.

[squabeggs]

Thanks! So, to be clear, if it is a bit low, I can just top it off with nothing but distilled water? or do i need mixed G12?
I'm gonna put all new G12 in when I do the timing belt and all that related mess in a few months...

[Mikewire]

Sure you can throw in a little distilled water to top it off no problem. You can never have enough bottles of G12 sitting in your garage

[Rennwagen1]

You can never have enough bottles of G12 sitting in your garage

Believe Mike when he says that!

I thought they blinked before the warmed up to temp? Maybe not!