I have a 2001 TT quattro convertible and I started having battery drain. I pulled the radio fuse and the draining issue went away. What exactly is it about the radio that causes the drain on the battery when the car is turned off ? Are the radio and amp and so forth all in a single unit and is it easier to just have to original radio rebuilt or just buy another aftermarket radio ? Is there a draining issue regarding the amplifier as well and is the radio and is the amp on the same fuse ?
Thank you for any help

 

I believe that you currently have the stock radio, amp, and speakers. Is that correct? Are there any aftermarket components or accessories attached to the system, e.g. Bluetooth dongle etc.?

This sounds like a problem where an aftermarket radio is installed incorrectly, such that the radio's 12V "switched" input (usually yellow, though I think in my TT it was red) is incorrectly connected to constant 12V. The 12V switched wire is controlled by the ignition, and it loses power when the ignition is turned off. Car radio systems, especially aftermarket radios, use this wire to determine when to turn off. Generally, they are still connected to constant 12V as well to enable radio memory etc. If you connected the switched input to constant 12V, the radio will remain on while the car is locked draining your battery.

You didn't directly mention it, but it sounds like you have the stock radio, in which case this shouldn't be an issue. The only possibility where the above issue could affect a stock radio is if the wiring was altered at some point when a aftermarket stereo was installed and removed by a previous owner.

I just checked the wiring diagram, and "J429 Central locking control unit" is also powered by the same fuse as the radio. Perhaps your issue lies there. I note that you have the convertible. Perhaps it could have something to do with the latch for the convertible top? I'm not aware of battery drain issues involving J429 for the coupe (not that they don't exist), but my first thought is an issue with a sensor that the coupe does not have.

These are the components that the fuse provides power to:
Radio
J429 Central locking control unit
J218 Combi-processor in dash panel insert - I'm not certain if it's the actual power source for the dashpod, but it likely is.

Here's a link to the wiring diagrams if you don't already have them:
https://drive.google.com/file/d/1DKC...usp=drive_link (not my Google Drive)
I got the above info from pages 3 and 5.