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89 560sec, 2002 e320w 4matic
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130 Posts
Discussion Starter #1
Something is draining my battery after 48-72hrs of no use. If I drive her everyday she's fine. Any thoughts? Btw I replaced battery and still having problem.
89 560sec

Thanks
 

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Premium Member
87 300SL "Roadster" 86 420SEL "Limo" 89 420SEL The "New" Limo 87 190E 2.6 fact bodykit
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1,575 Posts
Do you have an alarm system fitted?

My SL and one of my SEL's has an alarm fitted and it kills batteries within 3 weeks if I don't use the cars.

Now they sit on trickle chargers.
 

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89 560sec, 2002 e320w 4matic
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130 Posts
Discussion Starter #3
That's a great question. But Im not sure, only have the car for about 6 months. Is there a way to tell?
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,992 Posts
Lock the car with the window open. Then reach in and open the car from the inside, then try to start the car. The horn and lights will flash. You have the alarm.

The alarm controller is under the passenger side footwell access compartment. But it sounds like something else though. If you don't have the manuals, PM me your email and I'll send them.

Troubleshooting the electrical system can be tricky for even experienced technicians or Engineers.
 

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1983 280se
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40 Posts
Your local garage should be able to test for battery drain (2 minute job) - boot (trunk) light - glove box light - faulty alternator - good luck with it.
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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9,487 Posts
Easy way to find a short. Remove the ground cable from a fully charged battery, then hook up a test light (12V) to the Ground pole on the battery and clip the test light to the ground cable (not touching the pole on the battery. I have a test light that has asharp probe on one end and a clip on the wire(CarQuest has these), and I clamp the probe to the battery pole. . If the light is on, then there is a short. Open the Fuse box and begin removing fuses until the one you remove makes the light go out. That fuse is the circuit of the drain.
 

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1983 280se
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40 Posts
My old BMW had a similar problem, the leak was somewhere in the starting circuit - if the battery dropped a little bit of voltage there was not enough power getting to the starter motor solenoid - what I did was to run a wire from the starter relay to another relay connected to the battery direct to the starter solenoid - never had any more problems
 

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'95 993 / 2011 F150 Raptor SC / Land Cruiser D4D V8 / 500 SEC
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439 Posts
From the time you quote I'd say a lightbulb is staying on. Check the one in the trunk for starters.
 

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89 560sec, 2002 e320w 4matic
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130 Posts
Discussion Starter #10
I took car to my tech with this problem and he told me I needed new battery($200).
Since problem was mis diagnosed should I be responsible for cost of battery. Btw, battery he replaced was also new which I told him about.
 
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