battery problem?

Hi All,
Once again i find myself in need of assistance!

My wife had to get the car (02 mercedes c220 avantguard) jump started in the early hours of this morning (she'd just completed a night shift).
She stated that she'd noticed during the night that the interior light had come on (on its own) and the hazard lights had started to flash (no alarm so im guessing just the hazards) by the time she'd finished her shift the battery was flat.
Ive noticed over the last week or so that when the car is started from warm or from cold there is a clicking sound that can be heard from (i think) behind the center console (radio area). im not a car person but i think this might be a relay clicking? im wondering if anyone can shed some light on this as my wife works a lot of night shifts, shes a nurse so to have a unreliable car or a problem on the car is a no no.
the car started immediatley it was given power if that helps.
thanks all

 

I think we have 2 faults here, the clicking behind the dash will be a heater flap at fault.

Re the battery going flat its possible that the alarm siren has expired, upsetting the alarm, I would unplug it and see if it cures it

 

Many thanks for the post.
After the wife got home this morning and mentioned it to me - i went outside and again noticed the hazards flashing (although not switched on) - for some unknown reason, i left the car unlocked and kept my eye on it. its not happened since. could it be something to do with having the car locked?
Could it be the battery as the batteries been in it for at least 4yrs?
i intend taking it to a friend who has his own garage but i wanted to get some info first on possible causes.
thanks again for any assistance given..

 

sorry for the follow on but as im ignorant of such things - how would i unplug the alarm siren? is it as easy as it sounds? locate the siren and pull the plug out once found?
thanks again

 

You need to remove the rear section of the nearside front wheel arch liner and its under a plastic cover at the bottom

 

An update - apparently now when the car is locked with the key fob, the warning lights flash on and off as they should do - unfortunatley they dont turn off. They keep flashing. This happens immediatley upon the car being locked. Therefore the car has to be left unlocked.
My wife said that when she unlocked the car this morning with the key (as the battery was flat) that comes with the fob the car alarm went off.
do you think that your idea of the alarm siren expiring has now gained weight with this update?
i appreciate your helping me - thank you

 

I still think the siren has expired

 

I've just gone through the same thing, your does sound the same.
My alarm siren is presently removed, waiting on a replacement arriving.
All the problems stopped when I removed it.
Lots of posts on google on it, even you tube posts.
http://mbworld.org/forums/c-class-w203/388309-alarm-siren-battery-placement.html

C.

 

As above - the flashing hazards show the alarm is activated, and the lack of siren points us to the top suspect in this common fault.

 

Yes, a very common problem, and if you search your symptoms on this forum you will find many results with cases just like yours.

 

what can i say - thank you all so much. i really appreciate you all taking the time out to help me. thanks all