Had mine replaced in January at VW Poole, about £160, tried it a few weeks later and it didn't work, rebooked and took it in, at first they said I was using the wrong converter plug, so I showed them what I had, and eventually the Mechanic agreed that it was showing power but not providing power, He striped it all out, only to find that when it had been replaced it was wired the wrong way round by their previous mechanic, so It just maybe the case for you as mine now works fine, hope this might help.