XR5 Electrical drain?

[prh065]

Hi guys,
I have a 2008 MB XR5 that intermittently drops the audio menu from the dash and can drain battery power overnight. It loses all remote audio and phone control when this happens. Local dealer (who sold the car to us) has had it back and relaced combination switch and battery, as well as cleaned the earth points down right hand side of car. Problem still exists and will kill new battery if continues. Currently I am switching off all acc' at end of day but have had no audio menu on the dash or functioning steering wheel controls. Anyone encounter this before, and found a solution? I'm leaning toward a short in the audio unit. Any help appreciated.
Cheers.

[cobrin]

disconnect the HU connections and monitor for a few weeks. You'll need to remove the radio to get in behind it.

that's what I'd do for a start. Confirm with a Multimeter on a power draw with and without it connected. If no change then it's something else.

How to test.