I'm experiencing a strange behavior with my headlights. When using them in auto-mode, everything works fine. When I manually turn them on, they will illuminate but eventually (several seconds or minutes later) turn themselves off. Here is my setup:
- 2015 Audi Q7 TDI Prestige S-line
- LED bulbs installed in main projectors and in fog lamps
- No VCDS customizations implemented for headlamps.

I discovered this problem when driving one foggy/rainy evening where I switched over to manual-on and pulled the **** out so I could also use my fog lights. After a few mins my headlights shut-off and so I turned the **** to off and back on to auto and they turned back on. I assumed that perhaps my fog lights were the problem, and tested the system again later by manually turning-on the headlamps without fog lights and they also turned-off after a few minutes.

I scanned my vehicle with VCDS and don't see any stored error codes associated with the external lighting. Any suggestions?

 

That's pretty wild; you'd assume it would be just the opposite on the actual switch position (if the light sensor were involved), if you were going to have that type of issue unless it is simply the multi-function headlight switch itself has a loose/wonky electrical connection when set to the 'manual ON' position, which could explain why sometimes it is just seconds and other times they might stay on for up to couple minutes before they turn off. Best guess based on info provided.

IMHO, if it were the housings/ballasts/bulbs, or a relay or wiring problem, then the switch position shouldn't matter. I can't think of anything else offhand, but if there are ANY fault codes showing up not related to door handles (LOL! Yes, a Q7 electrical joke), then post them up for review. It's never good on this car to ignore or discount the existence of random seeming fault codes, and especially ones date-coded to precede or coincide with when you began noticing the headlight issue.

That said, not everything throws a fault code; if the control switch itself cuts the power due to an internal fault in switch, then you wouldn't expect to see a fault code...it's the source. I'd be curious to know if the DRLs or front/rear markers/running lights also go out when the headlight bulbs turn off. They wouldn't have to necessarily due to the switch design, but it's just a data point to consider if they do go off, etc.

 

Possibly just overheating. As heat builds, so does resistance. Reach a certain point, and the lights will go out. Alternatively, there could be a protection circuit in there that trips. I had an older vehicle that would do that.... had to replace the switch.

 

Makes sense. But seems odd that they never overheat or cut out on auto. Just manual on.

 

Right, but if it is a switch problem, then it might make more sense assuming there is a separate relay driving each circuit.