Low Coolant Warning Light in Cold Weather

[jaberoo]

This has been described before in posts but I haven't seen an explanation.
When the temperature is around freezing or below, the coolant CEL comes on even though the reservoir coolant level is at the maximum mark. If I shut off after driving no more than a mile and restart, it doesn't come on. This didn't happen the first winter I had the car but has happened each winter since.
Any ideas?

jaberoo
02 Jetta TDI Wgn, 97.5K

[Pelican18TQA4]

You need a new coolant temperature sensor, no doubt!

If you take the car to the dealer, they'll tell you there's nothing wrong because there won't be any codes or CELs. However, I can almost guarantee that the temp sensor is the problem. My immediate family has 3 (including a '02 Golf TDI) MkIV cars and all 3 have had bad coolant temp sensors with the exact symptom you describe.

[jaberoo]

[QUOTE]
You need a new coolant temperature sensor, no doubt!

Interesting, since I replaced the coolant temperature sensor only last summer. The original had failed, the CEL came on steadily, gave a code, etc.
In this cold weather thing, the light flashes indicating low coolant level in the reservoir. Both sensors (original, before failure, and replacement) manifest the same winter problem.
A puzzlement.

[Pelican18TQA4]

Hmm. When you replaced the coolant temp sensor last summer, did you replace it with the green-topped version?

[jaberoo]

Hmm. When you replaced the coolant temp sensor last summer, did you replace it with the green-topped version?

Yes, that's right. The Green one.

[Pelican18TQA4]

Hmm, well then I guess it's possible that you got a defective one or that there's another problem.