# Battery Drain (always)



## MotorCityMadMan (Nov 30, 2005)

_The car in question: 1976 Mercedes-Benz 450SEL. The problem: The battery is being discharged when the car is just setting (not running) There are no interior or exterior lights on. The battery cables appear to be in good condition.

Any suggestion ? _


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## bruiser (Jul 30, 2005)

My neighbor had a car that kept draining the battery. Turns out the clock in the radio way staying on. He thought the clock was supposed to be on all of the time.

Get a volt meter and attach it across the battery terminals. Begin pulling fuses one at a time. Watch the meter, and when you see a change, that's your supect circuit. Hope I said that right.


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## dai (Jul 2, 2004)

a faulty alarm/immobiliser will also cause it


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## buddycraigg (Nov 26, 2005)

bruiser said:


> My neighbor had a car that kept draining the battery. Turns out the clock in the radio way staying on. He thought the clock was supposed to be on all of the time.
> 
> Get a volt meter and attach it across the battery terminals. Begin pulling fuses one at a time. Watch the meter, and when you see a change, that's your supect circuit. Hope I said that right.


if i may make a slight adjustment to what bruiser said.

use a multimeter that can handle 10amps.
even the ones you buy at walmart can do that now days.

disconnect the positive cable from the battery.
put the red lead from the meter to the + connector on the battery.
put the black lead from the meter to the cable.

at 0.04 or less most batteries will last 2 weeks.
if you have a lower reading than this i would suspect the battery or a faulty connection with battery cables or grounds.

anything higher than 0.05 then you start pulling fuses.
have someone watching the meter and when it drops down have them yell.
now you know what circuit to start tracing.

post any updates.


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## buddycraigg (Nov 26, 2005)

and are you sure the battery is good?
a volt meter wont tell you anything, you need to put a load test on it.

a bad cell can let a battery charge very quick and then discharge just as quick just sitting there.

if you have a standard toaster with a pull down handle and you're not afraid i can give you some instructions on what to do.

never mind that.
i'll just wait for your reply


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## StressedDad (Dec 3, 2005)

"if you have a standard toaster with a pull down handle and you're not afraid i can give you some instructions on what to do."
.......hehe.lol.

1./ I'd suspect battery. How old is it?
2./ Might be a short circuit ( bare wire touching metal - check cables )

Swap for a known good battery,if it cures it,then u'll know your bats toast.

or charge the bat and dissconnect the leads for a week.
Then reconnect - If it won't turn the engine over when u reconnect,....it must be the bat.

If it tries,then dies,u've got a drain somewhere,prolly a short.


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## Mullet Man (Oct 9, 2005)

To know for sure if you have a draw, get a test light. Disconnect the (pos)+ cable and hook the test light from battery ground to the disconnected positive wire. If that light lights up bright, then you got a draw.


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## MotorCityMadMan (Nov 30, 2005)

_Yes: First thought was the battery,Did a long slow charge. After three days i was needing a jump after work [ 10 hour days ] So, i buy a new Interstate 700 C.C.A. / 875 C.A / 85 Month battery. The car sat for three days. Bam, dead battery. no lights, Cig lighter active. The car does have a clock [ Just don't think thats it ] This multimeter sounds like a good starting point. One good thing is the fuses are under the hood. Ckecked battery cables, seemed fine, I will go over battery cables again-take them off and do a good cleaning.


I have a very nice toaster with handle-please send instructions :laugh: _


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## bandit109 (Nov 1, 2005)

Another thought ----- I had a 72 GMC that kept draining the battery, was the cig lighter. The rubber gasket on the back had desintegrated . Replaced it & no voltage drain .


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## buddycraigg (Nov 26, 2005)

Ok, since you have a new battery I don’t think we need to bother doing a load test so forget about the toaster.

If a new battery went dead after 3 days then yes I think you have a draw.
Time to dig out the meter.
Most meters are set up with 3 holes for the test leads to be plugged in to.
The black lead is always plugged in to “COMM” 
The red lead for this test will want to be plugged in to the hole for the 10amp rating.
The other red hole is for normal testing of voltage, resistance and low amps.

Disconnect the positive battery cable.

Connect the red lead to the positive post on the battery.
Connect the black lead to the battery cable.

Shut all the doors, trunk, turn off the key, and if the hood has a light that comes on when it’s open, remove it.
You want the car to be in the same state that it would be if it was parked in your driveway.

Now how many amps are you drawing?
I’m going to want to know that when you write back.

Make a note of where each fuse goes.
Start pulling fuses one at a time, checking the meter each time.
When you get to the one that the meter drops to about 0.05 I want you to put the other fuses back in except for the last one.
This is to make sure that the last fuse is really the problem.
Once you find the fuse then we’ll start picking that circuit apart.

If you take all of the fuses out but still have a draw,
Temporally disconnect the meter.
Disconnect the wires to the alternator.
And plug the meter back in and see what you get.

if you still have a draw, i'm going to need a schematic to look at for fuseable links


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## MotorCityMadMan (Nov 30, 2005)

Ok, Back in the game.  Today I purchased a Craftsman Digital MultiMeter (http://www.sears.com/sr/javasr/prod...0&vertical=TOOL&pid=03482146000&bidsite=CRAFT) 

I'm Getting up to speed on MultiMeter operation and Specifications. One specification of interest is operating temperature (32 degrees to 122 degrees) This just may slow down the project. It has been very cold here as of late.


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## buddycraigg (Nov 26, 2005)

dont worry about the temp.
it can take the cold better than you can.
if you can stand to be outside, the meter will too.


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## MotorCityMadMan (Nov 30, 2005)

I can't believe I found my way back. :sayyes: Anyway, I sold the car. I used eBay. The car sold in three days.


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