Webasto kills battery

[Bargain Bucket]

Every time I set my Webasto to run in the morning, I come out to a flat battery. The battery (S5) is only a year old and has been drop tested OK at two different garages. So I'm confident the battery is OK. The car goes to sleep at night OK and current drain when in sleep mode is negligible. This supported by the fact that the battery is fine in the morning if I don't set the webasto to come on. Is there a known issue with the Webasto whereby it draws too much current?

[X5Sport]

There should be a protection system in the Webasto which stops it doing that.  It should cut off if the battery or fuel level fall below certain levels.

Sounds like your voltage sensing circuit is not operating correctly.

Richard