500E - 2 dead batteries in 4 weeks - PeachParts Mercedes-Benz Forum

hanfrac · #1 06-19-2003, 09:03 AM

In the past 4 weeks, I've twice left my car parked for more than 2 days without starting it. Both times, the battery has died. The first time, I replaced the battery, as jumping it and driving it around didn't help it.

This morning (after giving my 911 turbo some much-needed exercise for 2 days), I went to the car and it is totally dead. I have not jumped it or taken it anywhere for diagnosis.

Is a general MB mechanic the best place to get this resolved or am I better off going to someone who specializes in automotive electrical systems? Also, any likely points of failure? The one thing I have done is I've unplugged the MB alarm system that was under the front passenger carpet mat. I did that about 6 weeks ago. Could that cause a problem? I did it because it was misbehaving and I felt like I could live without the alarm.

Thanks in advance.

Frank
92 500E
Tampa, FL

Tobias MB · #2 06-19-2003, 10:00 AM

A friend of mine with a BMW 635 had a new stereo system installed and in the trunk the shop messed up with the trunk light. It would never go out but unseen by my friend b/c it was in the trunk compartment. His battery died in two days until the problem was found. So, check the trunk light switch and be sure the light goes out with the lid closed!
If the battery charges OK while driving then after parking it with a full charge pull the fuses and check for a drain with a DVM (digital volt meter). It should be easy to find if it drains this quickly. You may also have a defective diode in the alternator.

Tobias MB
4 MBs

Mark Herzig · #3 06-19-2003, 01:13 PM

When I had my 500E, the prior owner had this same problem. He repeatedly had it in to the dealer and finally they called in a factory specialist to diagnose the problem. There was a short somewhere in the system that has to be tracked down.

mike690003 · #4 06-19-2003, 01:50 PM

I have a 300E, but I had a similar problem, it turns out that 2 fuses were blown and somehow my battery was dying because of that, check for any blown fuses.

#5 06-19-2003, 02:02 PM

I had a similar problem. Check for a light on in the center console that illuminates the P-R-N-D. It seems mine was staying on, draining enough power to kill the battery. I hear more than one 500E has this problem.

bond

run.exe · #6 06-19-2003, 03:38 PM

Do you have a grounding issue?

This could be as simple (but elusive) as a bad sunvisor anchor-point clip - or as deeply buried as an alternator issue!

Are any of your fuses blown?

PS - I have NEVER heard of this problem, Mr. Bond!

mark cummins · #7 06-19-2003, 07:42 PM

If You have a 12v Test light you can Test the System for a draw..Remove the + Side of the battery and Install a 12v Test lite Inline ..The Test light WILL Light up if there is a Major Draw in the system..then Remove the fuses in the fuse box,then the Relays Looking to see if the test lite goes off.When it does go out You have found the Source then Find out what else is in the circuit ..
I have Seen Defective trunk lites..clocks..relays..and a Cigarette Lighter...That one kick My Butt ..several Hours..But I Found IT!
I Would try this before you take it to a Shop.

ItalianBenz · #8 06-20-2003, 12:56 AM

Han. Do you have any sort of consumers powering up. Can you turn the headlights on.

1.does anything come to life at all.

2.The factory alarm is tied into the starter lockout circuit.

3. Did it start before you disconnected the alarm.

4. What kind of state is the battery in.
5. Is it old has it been load tested.

6. How often do you drive your E.

7. Do you have any aftermarket consumers.
8. plug the factory alarm back in
9. Try disconnecting the factory antenna in the LR trunk area behind the panel,these have been know to draw excessive current over time. Not saying this is the culprit. But its a good start. Good luck

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