Battery drain... Again.

[Starky]

Hi guys,

I'm having a problem with my car draing the battery, if I don't drive it for a day.
I've taken it to one garage who had it down to the alarm siren and subsequently replaced it. But the problem returned.

I since took the car to a friend of mine who is a general mechanic, he ran some tests and found the alternator at fault. On ordering the new alternator he ran the same test and found all was well..... Strange

So his advice was to see an auto electrician.

So my question... Does any one know of a good auto electrician (preferably a merc spealist if there is such a thing) in and around the London Borough of Richmond

Please help as I really need this sorted.

 

[Neil Mackay]

Seats? Big drain to do it overnight so seats or command not shutting down (if you have command) try pulling the seat fuses then add them back in turn!

 

[joecash]

good old detective work with a multimeter (ammeter), looking for current drain, is called for - if not you will spend a fortune on other peoples guess work - you probably need the services of a good auto electrician - your local reputable indy will surely know of one - steer well clear of the mb main dealers or your pockets, imho, will be empty before you know it.

 

[Starky]

I've tried that Neil, and no luck. Really starting to annoy me know.

 

[Danny DeVito]

First stop is measure current leaving the battery. Take pos lead off and check current draw with multimeter. Thats with key out. Just to see what kind of drain you are having. I presume that battery is new is it ? After that maybe go to your nearest fuse box and with meter still reading current at the battery start pulling fuses. Hopefully you will find one which drops the current. I dont know how many fuse boxes are in your car so try find out. Maybe doing that will point you in the right direction. My old car was a Trajet. Sometimes the electric window button got stuck down and killed the battery. Though the Trajet was a little less complicated than MBs

 

[jamesfuller]

A tip when cheching the drain. I had to do this with a BMW I owned. Roll all latches to the closed position (doors/bonnet/boot open for access though) and lock the car. It will probably take 10-15 mins for all the control units to go to sleep.
You should be able to tell when this happens as the reading on the multimeter should settle down. Once this happens (may be different on your car I'm not sure) Take photos of where the fuses go. then pull them one by one and check if the draw changes each time.
The reason i said take a photo is because once you remove a fuse, leave it out. Putting it back in may wake the system up again and mess with your readings!

When I went through this, I got down into the foot well to start pulling fuses and felt a slight breeze, the heater was very faintly still blowing (caused by a faulty heater resistor)

Like I say, this was a Bmw, a Merc may be set up differently. I have never had this problem with a Merc. Just trying to think of ideas to help but I don't want to lead you up the garden path. Hope this proves helpful!