View Full Version : Mercedes wagon problem

Rich VanValkenburg
07-09-2007, 08:16 PM
Certainly not my own car, it belongs to the folks where I'm doing a remodel. This car only gets driven once or twice a month. It's a 2002, with 22,000 miles. It drains new batteries after two weeks of being left in the garage. It's never done that before, and the Mercedes shop told them it's normal and they have to drive it every day. It's a guest vehicle. My employer is wheelchair bound and has a special vehicle, so the wagon is left for visiting family and friends.

What would cause it to drain new batteries that quickly? Are the Mercedes dealer techs out of their minds?


jack grebe
07-09-2007, 08:20 PM
What would cause it to drain new batteries that quickly? Rich
different sentinal systems....clocks, alarms,radio,etc.
have them pick up a battery maintainer and keep it plugged in till it is needed

Ian McColgin
07-09-2007, 08:21 PM
Of course they are out of their minds and an incredibly bad dealership. Contact the company.

The diagnostice is pretty simple - put a sensitive ammeter on the plus side of the battery and start poking.

My bet's on a faulty ignition switch that leaves something closed but better to start systematically.


Bob Cleek
07-09-2007, 08:54 PM
Yea, I've got a 2003 and no problems, although I haven't left it sit for two weeks, either. Try cleaning the battery terminals for openers. Don't know why, exactly, but dirty terminals can leak juice. Most newer cars have all sorts of computerized crap that runs all the time anyway. A trickle charger may be just the ticket.

07-09-2007, 09:02 PM
When the car is driven, is it driven long enough to recharge the battery? If the battery and charging system are good, 2 weeks should not bother it. Seems like something may be stuck on. The dealership is full of crap.

07-09-2007, 10:20 PM
Don't know the answer, but try this forum. I have sorted out a few issues with mine via this route.
Benzworld http://www.benzworld.org/forums/forumdisplay.php?f=23

Rich VanValkenburg
07-09-2007, 10:22 PM
I'd heard something about the sentinel systems. Aren't they supposed to go off after a certain amount of time of inactivity? Can't say I suspect the battery terminals now after getting two new batteries in the last month. This dealership went through the maintance schedule and replaced everything listed, plugs, all filters, brakes!!, new synthetic oil, you name it, all after just 22,000 miles since 2002. Unbelievable. They saw a wheelchair coming and hit her good. But they didn't fix the real problem.

The only system I suspect is Onstar. It was deactivated, but still looks like it's monitoring. I don't know about others.

Katherine, can you recommend a better Merc dealership? This car is up in Bloomfield and the dealer is close by but I don't know who it is.


Bob Smalser
07-09-2007, 10:30 PM
What would cause it to drain new batteries that quickly?

Are the Mercedes dealer techs out of their minds?

A short.

And yes. They are putting your friend off probably because shorts can be difficult and expensive to find and fix.

Worn-out batteries...as in any battery over 30 months old...also exhibit the same symptoms. So if these are new, we go back to diagnosis #1.

You could practically run a full-sized laptop computer for two weeks on a large car battery.

The Bigfella
07-09-2007, 10:55 PM
I have had a problem like that with a car before. Lots and lots of systems still run voltage after the car gets switched off - in my BM's if you sit inside you can hear stepper motors shutting down the ventilation system one after the other for a couple of minutes.

You may have something as simple as a stuck door locking actuator or stepper motor. I'd bet the Onstar draws a bit - an glovebox lights can do this too. The way to do it is to shut the car off and check each and every fuse circuit one at a time for current draw - and there will be a few that have fuses away from the fuse box too. I'm assuming the fuse box is still up front on the Mercs? If so, tape down any switches that may be open when the bonnet (hood) is up while you go through with your multimeter. A $10 digital multimeter will find it for you.

This car is a bit young for another problem that sometimes occurs with wagons - the wiring harness in the 5th door flexes a lot and can wear through and create a short there.

Dan McCosh
07-09-2007, 11:11 PM
The standard for leaving a car is about 30 days--the so-called airport demand for batteries. Two weeks is too short.

07-09-2007, 11:56 PM
The vehicle manual ,electrical troubleshooting section should state an acceptable range of 'parasitic' battery current drain. The good news is modern electronics are thrifty with power , the bad news , is there is an increasing amount. A VOM with a current-measuring range , inserted in series with a battery terminal and a (removed!) battery cable , should give an objective indication. Microamps=good , less than , i think about 50 miliamps =acceptable.

All above advice is good , and relevant ... a bit of troubleshooting , good connections, maybe a charge-maintainer or a Perko battery switch {if mfgr allows} ought to address the trials.

The Bigfella
07-10-2007, 12:41 AM
A battery switch will kill the car's memory - things like radio codes, engine fault analysis, etc.

07-10-2007, 07:00 AM
my bud once had a trunk light stuck on , would kill the battery overnight

clean the gnd connection to the terminal , engine block and the firewall, could be the batt is low but not dead , a thermal wrap might help if the batt is stored in the cold , iirc vw has a blanket

found out the other day a sure fire way to zap a battery is to store it sitting on a concrete floor


in the winter i use a solar battery saver on the cig lighter , puts out ~ 1 watt , enough to counter the leakage and keep the batt up for longer

jack grebe
07-10-2007, 07:26 AM
found out the other day a sure fire way to zap a battery is to store it sitting on a concrete floor

That's BS. What a battery is sitting on has nothing at all to do with battery drain.

07-10-2007, 07:40 AM
That's BS. What a battery is sitting on has nothing at all to do with battery drain.

wrong :D:rolleyes:

07-10-2007, 09:02 AM
My parents have a Toyota Tacoma with a similar issue - 2 weeks unused and a dead battery. They got out the milliammeter and found that with the key in the ignition there was a significant drain, but with the key removed the drain was insignificant.
They didn't bother to diagnose further - just made a habit of removing the key.


07-10-2007, 10:34 AM
Please explain how a battery, out of the car, can discharge, or not, depending on what is resting on.

Rob Stokes, N. Vancouver
07-10-2007, 10:52 AM
wrong :D:rolleyes:

'tis true - the concrete floor thing is a myth - no truth to it at all.

However - there's a perceived truth, and there is some credibility to the perception. The ability for a battery to release current is directly proportional to it's temperature. Generally speaking, when a battery is stored on a concrete floor it's stored in a garage or other unheated space. The concrete is often colder than the air but it's also far more conductive as far as heat's concerned and can "suck" the heat out of an otherwise warm battery.

Therefore it's possible that a battery sitting on a concrete floor is in fact colder than that same battery would be if it was sitting on a piece of wood or raised off the floor and as a colder battery will not release it's current as readily as a warm(er) battery, so starts the myth that a battery stored on a concrete floor loses it's charge.

BUT (and it's a big but) - there is absolutely no (NO) scientific proof that the surface on which a battery is placed has anything whatsoever to do with the charge in that battery unless there is an electrical line somehow established between the two of them (battery and base). In which case, all bets are off.


07-10-2007, 11:06 AM
I don't usually deal with Mercedes dealers so I can't really recomend one. There are, however, several in the metro area. However, I would call up this dealer and complain VERY loudly to the service manager about your friend's treatment. Keep calling and complaining until it gets results. I'd call Mercedes' customer service line too.