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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 11-11-2013, 12:56 AM   #1
84CopperGT
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Default battery keeps dying

I got a brand new battery Saturday night. Started the car up and let it idle for about half an hour just to make sure the battery worked. I haven't touched the car since then. I came down to crank it up and the battery is completely dead. It won't even turn over. At first I thought maybe the alternator was bad but since it killed it while it wasn't even running Ihave no idea what it could be now. Does anyone have any ideas? I am at a total loss.




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Old 11-11-2013, 01:58 AM   #2
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somethings pulling power when its off. after market radio wired wrong etc?
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Old 11-11-2013, 02:04 AM   #3
84CopperGT
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I am thinking radio or ignition now. I unplugged the ignition from the starter solenoid, set it on an autotender and will see in the morning. But I would ace bets that its still dead.
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Old 11-11-2013, 06:57 AM   #4
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you need to perform a parasitic draw test to isolate problem
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Old 11-11-2013, 11:14 AM   #5
84CopperGT
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Its not the ignition. I have a neighbor saying voltage regulator. That's the badly corroded thing under the starter solenoid right?
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Old 11-11-2013, 11:52 AM   #6
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Not the voltage reg. You have a draw on the battery when car is sitting. As stated above, throw a volt meter on your battery and start pulling fuses to see where the draw is, or at least narrow it down. First thou, if you have corroded connections, clean those first. Good luck
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Old 11-11-2013, 11:59 AM   #7
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There is a draw coming fron the regulator though. That's the only place I could find a draw. I used a test light and it was the only thing that lit up
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Old 11-11-2013, 12:29 PM   #8
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If your autotender charges at 1A it will take about 75 hrs to charge your battery. If it charges at 10A, you'll need about 8 hrs to charge your battery up all the way.
When you can start it, turn on the lights, heater fan, wipers, and check the battery voltage-it should be between 13.6 and 14.5. If it is lower, check all of your cables and the alternator.
If your fully charged good battery loses it's charge in 8 hrs, you have a lot of current being drawn out, about 10A. A light will not be much help finding a parasitic draw, a current meter or clamp will be much more accurate. If you disconnect the battery cable, insert your current meter (make sure it can read 10-20A) and wait about 15 minutes. You should have under .1 A draw. (do not try to start your car with a current meter in series with the battery) . after 15 minutes if the current reads above .1A, you can start removing fuses to see where the draw is. When you remove the fuse to the problem circuit, the current meter reading will drop to approx .1A.

Always clean your battery terminals and cables with a circular brush everytime you take them off.
If the terminals are dirty, your battery will not charge properly.
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Old 11-11-2013, 01:32 PM   #9
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It was dead in under 24 hours. So I am looking for around a 3A draw minimum. If my math is right.
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Old 11-11-2013, 10:26 PM   #10
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Quote:
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It was dead in under 24 hours. So I am looking for around a 3A draw minimum. If my math is right.
go get a dang multimeter and see what the draw is and stop freakin' guessing...........pull fuses until the drain is under 25-50 milliamps then get a diagram of the circuit the fuse you pulled and unplug components in that circuit until drain is gone......don't make a mole hill into a mountain here!
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Old 11-11-2013, 10:26 PM
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