Audi Q7 and Philips LED 921

I'm having an issue with the PHILIPS 921 LED, in a 2014 Audi Q7. They just barely illuminate when installed, but are bright when connected to a 12V battery. The car doesn't give a "lamp out" notification with the LED installed. Does anyone have any idea what the issue is?

Re: Resistor Needed for LED Back-up Retrofit?

It may be that the reversing lamps aren't on a supervised circuit such that it notifies the driver. You can test that by removing both reversing lamps and then seeing if the "lamp out" indicator lights. You might need to start the car and put it in reverse just to be sure it activates the supervisor function.

If no such indicator lights up, it may still be that it's a supervised circuit but without notifying the driver, in which case it may just issue PWM voltage to keep rechecking the circuit-- an open short doesn't always mean a burned out bulb. More likely, though, is that you just need to reverse the bulb in the socket. If you get the same results, Philips does have a load resistor that may solve the issue, sold as a "CANbus Warning Canceller".

If I may suggest bulb in socket but not installed in lamp and check brightness. Maybe not working well in the housing?

jzchen said:

If I may suggest bulb in socket but not installed in lamp and check brightness. Maybe not working well in the housing?

Click to expand...

Certainly that is a good suggestion. Those Philips LEDs seem to work quite well in a pretty broad range of vehicles, but maybe yours is an anomaly. But if it's just a feeble glow, not an intense (but very scattered) display, then it points back at electrical. I'd have to look at the details of that lamp assembly to state categorically that it's a 'pattern' issue right off the bat.