A3 Coolant Warning Light: Meaning & Fix

Hello.

Eine Freundin von mir hat ein A3 1,9 Tdi PD 74 KW (AXR). Nach dem Starten leuchtet während +/- 30sec im FIS die rote Alarmleuchte für Kühlwasser (Überhitzung). Danach geht sie dann aus und es ist alles normal während des ganzen Tages. Ich dachte dann an den zweiteiligen Temp-Fühler und tauschte den dann, leider ohne Resultat, ausser dass er jetzt, nach mehrstündigem stehen, auch während par Sekunden leuchtet, dann aus geht. Die Temp-Anzeige funzt wie gehabt richtig (90°C). WassThe first one is okay.

Does anyone have any ideas on how I can further test and measure this?
Can a VAG diagnostic tool be used to perform a diagnosis (even if there are no error codes in the fault memory)?

Thank you for all the information.

Hi,

In your coolant reservoir, there are likely two sensors that are not detecting enough water due to the coolant's conductivity. The coolant itself is slightly conductive.
Try cleaning the two pens with a toothbrush to remove any residue that might be causing them to not work properly.
It might also be a good idea to change the coolant occasionally, especially if there's a buildup of deposits.

Unfortunately, VAG-COM cannot currently detect the coating on the pins, perhaps in a later release with image processing and a Robo-Cam .

Best regards, Rainer.

Rainer K. wrote:

VAG-COM unfortunately cannot recognize the coating on the pins, perhaps in a later release with image processing and a Robo-Cam

.
Hi Rainer,

When can we expect this release?

Hello Rainer and Ulf,

I don't know why you're making fun of me, but I still want to thank Rainer, and I will be testing this out over the weekend.

Regarding my question about the VAG-***, I was thinking more about reading the values of the sensors or testing the engine control unit (ECU), but first, I'll start with the simpler things as Rainer described.


Thank you again.

Hi,

Come on, there has to be some fun. Possibly, there is a measurement block where a corresponding resistance value is displayed, but I'm not sure about that.

Best regards, Rainer.

Okay, I have to say, "Respect!"

Last Saturday, as described here, I cleaned the two sensors in the water reservoir with a toothbrush (as best as I could). Afterwards, I rinsed the reservoir with water and refilled it with a G12 mixture. Fortunately, the light hasn't come back on since then!

Thank you again.