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Discussion Starter #1
My father have a 1989 300E and trying to help him resolve what causing his battery to drain.

Something is draining the battery and I need help.
The battery is less than a year old and was tested good by Autozone. The alternator was replaced last week so I don't think that is the cause.

Today I took out all the fuses. The battery had a reading of 12.18v at 1:23PM. At 1:53PM the battery voltage went down to 12.16V so it looks like something else is draining the battery. I don't know where to start. Please help
 

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2008 E350 4M, 1988 300TE
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5,432 Posts
Well to start off, 0.02v drop is not an indicator of anything. Plus, 12.68v is a fully charged battery.
 

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Discussion Starter #3
The battery was fully charge last 4 days ago with a reading of 12.68. I will test the battery again in a couple of hours and let you guys know.
 

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'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
I had the same issue.
Charged the battery to the max, it took the charge, but it could not hold it.
It was dead the next day.
Took it to be checked, confirmed that it could not hold the charge, got a new one, never looked back.
 

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Proton Saga BLM
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64 Posts
My father have a 1989 300E and trying to help him resolve what causing his battery to drain.

Something is draining the battery and I need help.
The battery is less than a year old and was tested good by Autozone. The alternator was replaced last week so I don't think that is the cause.

Today I took out all the fuses. The battery had a reading of 12.18v at 1:23PM. At 1:53PM the battery voltage went down to 12.16V so it looks like something else is draining the battery. I don't know where to start. Please help
Battery Leak test!
To perform current leak test,use an amp meter to check,disconnect your battery NEGATIVE cable,ignition off,close all your doors except bonnet,and radio player.
Connect the meter RED lead to the DISCONNECTED cable.
Connect amp meter BLACK lead to BATTERY NEGATIVE terminal.
Your amp meter will indicate more than 3amps.
Disconnect the fuses one by one,and monitor the amperage indicated.If the value drop rapidly,you may go through what is happening there.
 
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