DxbStew

Hi all,

I've had a battery drain problem for the past 2 years or so on my 2001 CLK55, and I've had no luck solving it.

If I don't drive the car for a couple of days, the battery goes low, and doesn't have enough juice to crank the engine. I've been through 3 batteries, the last on bought a few months ago, which is in good condition, as I was driving 120km per day working on my last project.

Now I don't drive as much (I work at home these days), so I have time to try to resolve this.

I used an ammeter and measured the current when the car is locked, and alarm active. The current settled down to around 50mA. It was the same for 30 minutes. This suggests that something is acting erratically, and consuming current randomly, which is very hard to trace!

I did a lot of research, and came across a common problem with the alarm siren battery, where the battery fails and can cause erratic current consumption. I disconnected this yesterday, however, this morning (20 hours later), the battery voltage had dropped 0.7V, from 12.7 down to 12, so it appears the siren isn't to blame.

Another common problem is the seat controllers. However, my understanding is that if one is faulty there would be a 700mA draw constantly, so it appears that this isn't the problem.

I also removed the fuse for the phone, but this didn't resolve it either.

Anyone any ideas or thoughts?

Cheers

DXBStew

Plutoe

You either go fuse by fuse or purchase a CAN Bust tester or find someone with MB SDscan

GatorMB

The alternator voltage regulator was first thought, next a battery going stale.

These problems get complicated on the internet. the more information and tests performed will help a lot.
Start simple having the battery load tested first.