Low Battery Voltage - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 11 Old 12-21-2011, 01:57 PM Thread Starter
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Low Battery Voltage

So...I'm still having problems with voltage after doing most of the usual stuff (new battery, alternator, alt plug, battery cables, fusible links....). Wondering if you guys might have any other ideas to try. 1998 cobra convertible 5 speed, all stock, 90K miles...

The instrument cluster gauge reads just above the minimum (N on the word NORMAL on the gauge) and the battery light will flicker but never stays on more than a few seconds. Checked voltage at the battery, getting around 12.4 at 1500 - 2000rpm. Hopefully related - I've just started noticing the oil pressure gauge starting to jump around slightly, which is making me think it is something in the cluster itself that is going bad. Anyone ever have a charging problem because of the instrument cluster???? (Hopefully it isn't the alternative - for sale, one used cobra, new battery, blown engine )!!

Thanks everyone!!!

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post #2 of 11 Old 12-21-2011, 05:58 PM
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Have your alternator and battery tested. Sounds like one of them is bad. Your voltage output with the car idling should be between 13.4-14.4. Check for corrosion around the terminals as well as solid connections from the power cables and ground wires to the chasis

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post #3 of 11 Old 12-27-2011, 11:36 AM
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The gauge needles are behaving strangely because of the voltage issue, not the other way around.

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post #4 of 11 Old 12-28-2011, 08:47 PM
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As stated above Have ur alt tested. Your alt at idle should produce voltage around 13.5 to 14.5 if below 13.5 it is not charging ur battery enough and slowly draining the battery even while running.. Engine off all acc. Off key out ur battery should show 12.7 that is a fully charged new battery or should be anyway. Battery Voltage and State of Charge:

12.68v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%

If ur alt test good and ur battery is showing the correct voltage check ur body grounds, and battery ground I had the same problem and it ended up being cheap battery post replaced with some bronze end and solved my problem hope this helps
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post #5 of 11 Old 12-29-2011, 06:05 PM Thread Starter
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Thanks guys! I'm going to have a different shop check the alt and battery, auotzone said it was ok but I'm beginning to wonder. The cables are new but just standard cheap autozone aftermarket, I'll upgrade those while I'm in there. I'll follow up soon with the cure. Thanks again everyone!
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post #6 of 11 Old 12-29-2011, 11:22 PM
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Check your grounds too - remember its a relative voltage.
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post #7 of 11 Old 02-02-2012, 12:25 PM Thread Starter
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I had the alternator and battery checked again, different shop, no problems found. I put on a new ground (heavier gauge) from battery to block, and also a new heavier gauge from block to frame on the same stud (the one behind the oil filter). I hit the key, starter solenoid clunks...nothing. Is it possible that the starter went out while it was sitting there??? Or, am I missing something obvious??? Thanks!
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post #8 of 11 Old 06-17-2012, 10:15 AM
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im having the same problems with mine! i know its running off the battery .because with the car running i can unhook negitive battery cable and car dies!!alt is good and have tryed 2 new batterys
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post #9 of 11 Old 06-17-2012, 10:34 AM
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Assuming your battery is completely charged, that sounds like your starter died.

'94 GT, White, Cobra hood & bumper cover, '95R wheels
393w, Vic Jr 60cc, XE282HR, Victor 5.8 EFI, 80# injectors, Hooker LT 1 3/4 to 3", Borla proXS
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post #10 of 11 Old 06-18-2012, 11:44 AM
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With a DVM try this and note the results



1970 Mach 1 Mustang with SoT bilsteins and mid-eye 4 1/2 leafs 620lb drop springs in the front. *393 4V cleveland with Buddy Rawls custom solid cam Astro A5*
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post #11 of 11 Old 06-20-2012, 10:08 PM
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I know when i had a volt gauge mine read about 14.5 volts when running, the stock gauge stayed about mid way point all the time. You could try crossing out the starter solenoid with a screwdriver on the starter to rule that out.
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