Preheat LED On? Troubleshooting Engine Warm Start.

Hello,
I suppose it's not normal for the LED to briefly light up even when the engine is warm, right? I certainly don't experience that with older diesel engines. What could be causing this? The preheating time varies depending on the engine temperature, but the LED always comes on when the engine "starts."
The temperature sensor shows normal or plausible values when checked with VAGCOM. Is there any other meaningful check that can be performed?
(Maybe there's a clue about my cold start problem here...)

Greetings.
Carsten (AFN engine from Passat 35i, manufactured in March 1997).

carstenAFN wrote:

I suppose it's not normal for the LED to briefly light up even when the engine is warm, right?

Hi Carsten,

Yes, it's normal for the TDI. It's probably a warning light or something like that.

Hi,

The LED for the pre-glow function is currently not positioned parallel to the candles, but is controlled separately. This allows the main system (MSG) to use it for error messages and also as an indicator for the self-test. However, this only works if the LED is functioning correctly, as Ulf mentioned, so it will be tested.

The brief flash indicates that everything is okay, and it informs the engine computer about the power flow, ensuring that the LED itself is also functioning correctly.

If you want to monitor the glow plug function, simply (like Ulf, me, and probably others) connect an LED with a resistor in parallel to the glow plugs or the preheating relay.

Best regards,

Jan.

Thank you for the information; it's always reassuring when something is "normal" .

Greetings.
Carsten.