They turn on but are way too dim, like it has insufficient voltage going through them?...they dim as they should when your main lights come on but at that point they are dimming to such a level you can only just see them!
Check the two videos in the link, these should be burning super bright, have they been incorrectly wired?...any ideas?
Audi A6 - DRL's Fitted But Low Visual Output? - Peter.N.
If only one was faulty I would suspect the unit but as both are either there is something wrong with the design are they don't have a full 12v supply, check the input and make sure its at full battery voltage.