NSL sometimes just lights up for no reason!

Hello everyone.

'Recently, I've been having a small issue with the rear fog light on my Audi 80 B4 Avant. Occasionally, the light comes on even when the switch is in the 'OFF' position! This is indicated by the illuminated warning light on the switch itself.' When I then switch the toggle to the 'ON' position, nothing happens - the light stays on, and the indicator light continues to glow.
Okay, here's the translation:

'But here's the thing: When I open the tailgate, the lights go out as if nothing happened. If I close the tailgate again, they sometimes stay off, and they also don't turn back on while driving.' However, there are also times when I have to close and reopen the lid several times before the lights finally go out completely.
I've already checked the light bulbs for loose connections, and I'm ruling out a faulty switch because the lights go out when I open the lid.

Does anyone have any advice for me about what this could be?!!

... Connecting various wires within the cable harness to the tailgate.
I'm not familiar with your car model, and I don't know if the taillight assembly is located in the trunk lid or in the fixed rear section, but when you encounter problems like this, it's often due to frayed or damaged wires in the bend area of the wiring harness for the trunk lid.

@Andy:
Thank you for the tip.
You might be right, because the NSL (National Security Letters) are kept in the file. But is there always voltage running through the cables, even when the switch in the cockpit is turned off?
I'll still go ahead and remove the rubber grommets and check the cables.

... logically, there is only voltage on the wire connected to the NSL when the NSL is also switched on.
But what if a wire that is constantly connected to positive voltage (e.g., the trunk light) sometimes makes a conductive connection with the wire leading to the NSL (Night Security Light)? At that exact moment, you need to open and close the flap until the two wires are separated.
Check the crevice; you're sure to find something there.

See you later.

Andy.

I don't know exactly what your light switch looks like, but I'm guessing you need to pull it out twice for NSL? I also have a B4 (but a Passat), so it should be similar...
Okay, blah blah blah.



I just wanted to mention that the indicator lights on the switches seem to be malfunctioning. For example, in my case, the parking light indicator comes on when I turn on the high beams.


So, don't pay too much attention to what the warning lights are trying to tell us...

Hi,
The LED indicators for the fog lights are 'simpler' than the ones for the daytime running lights (I just had to disassemble a headlight switch because I couldn't get the light bulb out any other way).
The fog light circuits are permanently connected to ground and receive positive voltage directly from the lamp outputs via a 220-ohm resistor. There are still a few SMD components in the circuit path (a transistor with its control circuitry) during the parking light check.
I would strongly recommend taking a close look at the wiring harness, especially at the point where it bends.

Best regards, Rudi.

@DocSnydor:
Unfortunately, the light switches in the Audi B4 are separate and cannot be controlled with a rotary switch. I have my own switch in the center console for the navigation system lights, so the switch really only needs to perform one function... I'll still take a look at everything over the weekend and then let you know...