Battery going flat

[rhino]

Hi guys
I have had my Mercedes e270cdi estate now for just over 2 years it has rear air suspension if I leave the car for more than 2 days the battery goes flat. I have replaced the battery but it still does the same. Any ideas anyone. Thanks

 

[BlackC55]

You have a current drain.
Common item is the alarm siren.
The drain needs to be measured firstly to see what you have. Plenty of vids on you tube about how to do it.

 

[rhino]

I have tried the alarm siren and it's OK.
I've put a meter on it and it doesn't seem to show any drain that's why I'm confused on it.

 

[BlackC55]

What value did you have?

Is the alternator any good?

 

[rhino]

Alternator is OK
Can't remember the values I will test it all again this weekend and see what I'm getting and will make note of it

 

[Flyinspanner]

Reverse drain through alternator diode pack, (will still output ok) - would need to be tested.
Or

Use a clamp meter to check battery drain ampage.
Pull fuses on by one until drain disappears... there’s your culprit.