Could it be as simple as needing a new battery?

Discussion in '2005+ Mustang GT 4.6L Tech' started by BoatsHateMe, Jan 13, 2022.

  1. BoatsHateMe

    BoatsHateMe Junior Member

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    Picked up the 2008 Shelby GT about a month and 1/2 or so ago. Drove it home and parked it in the garage until spring. I've started it occasionally without issue. Tonight I went out to start it and it was flat dead. The battery is a red top Optima. Cables are spotless.

    I tried jumping it with my booster pack, I got nothing out of that. Hooked up my charger and as soon as the battery started taking a charge lights flickered on of off - dimly on the front hazards/blinkers (possibly rear too but that was still covered), the horn was intermittently squawking weakly, all without the key in. After about 20 seconds the horn would quit squawking but there were still electrical surges I could hear. One intermittent buzzing i heard was coming from the trunk. After opening the trunk I isolated it and it was behind the right trunk liner on the rear quarter panel, right behind the fastener that secures the liner to the trunk. I did not pop this out to see what was behind it.

    Once The battery charged for a bit I gave it a whirl again. Electrical was still pulsing and buzzing and when I put in the key and turned it everything lit up and was pulsing/buzzing. The engine did not crank at all when the key was turned, nor did it click like it was trying. Turning the key off and removing then other things including the horn and blinkers would buzz and squawk at me. I had to disconnect the battery to get it to stop.

    I've not yet tested the voltage. Not sure I can find my tester but I will put the charger on it overnight, disconnected and see where that gets me in the am.

    Here is a video of what it was doing. Any thoughts on how to approach this?
     
  2. jewc75

    jewc75 S197 Junkie S197 Team Member

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    Optimas have gone down in quality. Years ago when they were made in the US they were great, now they are junk. I have 2 yellow tops in my Peterbilt that are 2 years old and junk.
     
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  3. crjackson2134

    crjackson2134 Member

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    You need a fully charged (known good) battery before you can do any diagnostics. Yes, the battery alone could cause this.
     
    CGGuy09 likes this.
  4. BoatsHateMe

    BoatsHateMe Junior Member

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    Can you recommend a good alternative?
     
  5. dark steed

    dark steed Resident noob

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    What he said!^^
    I just went through this, it was indeed the battery. The car had sat for several months, so I jumped it off and that kept it charged for several days. I returned to the airport and it had died again, I got jumped off and drove 70 miles home. It would not crank when I got home. I put it on the charger overnight and tested across the terminals. All it took was one turn of the key to completely kill it again. I also had the associated horn and buzzing noises. I replaced the battery and it has been cranking fine ever since.


    Sent from my iPhone using Tapatalk
     
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  6. Pentalab

    Pentalab forum member

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    What's the date code on the battery ?? You need to put a digital voltmeter across the battery terminals.
    When you install the new battery, mark the install date on the battery.

    Once the eng is started, measure the voltage, right across the battery terminals. Mine reads 14.75 vdc with car idling. 12.3 vdc with eng off. If you don't read 14.75 vdc with eng idling ( say it reads 12.3) then the alternator is fried.

    Your battery is probably toast. How many miles are on the car ?? Typ you only get 5-7 years from a battery.
     
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  7. BoatsHateMe

    BoatsHateMe Junior Member

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    Couldn’t read the labels to see a date code, most everything is faded or worn off strangely enough. There are no punches or etches.
    Car has 36,800 miles.
    I’ll grab a new battery tomorrow.

    My fear, and main reasoning for going out and starting it, was mice. Bastages don’t need to get in there and chew up harnesses etc.
     
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  8. 86GT351

    86GT351 forum member

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    This
     
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  9. Juice

    Juice forum member

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    Ex optima fan here. The trouble free use I got out of a yellow top optima was 4 years. Than they started to go down hill.

    I bought my first walmart battery when my optima left me stranded on vacation. I currently have 3 Everstart batteries. One came in a car we bought. Dated 2013. Yes, 8 years old and still going strong. Starts fine in this cold weather, we had single digit temps. The one I got on vacation, 4 years old. I had to put a new batt in mustang when I did the EPAS swap. The battery harness and EPAS fuse setup would not fit the yellow top.
     
    Last edited: Jan 14, 2022
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  10. cavero

    cavero forum member

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    I've had this happen with optima batteries before, so I'd say it's pretty safe to say it's the battery. Been through 2 that lasted 4.5 - 5 yrs, and when they went, it was like they turned some kind of corner and just wouldn't hold a charge anymore. You could put them in a charger for days and sometimes they'd come back, in which case it'd be dead again if you let it sit for a day off the charger.

    I was pretty disappointed in Optima after how bullet proof AGM batteries have been for my bike compared to flooded lead acid batteries, so now I'm using a regular old flooded Interstate battery. Sucker is heavy but way cheaper and more reliable than Optima
     
  11. Juice

    Juice forum member

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    I believe they sulfate and lose capacity. Or develop an internal drain somehow. I do not let my batteries go dead, and it did not help.
    Oh crap, I forgot about the 4th Everstart battery in my 91. The interstate finally died after 12 years.
    I would go Interstate, those have been good for me too, but lost my supplier.
     
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  12. jewc75

    jewc75 S197 Junkie S197 Team Member

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    Any battery made by Penn. Almost every gold battery at Walmart, parts stores are made by Penn. Deka is my goto battery, also made by Penn.
     
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  13. LikeabossTM

    LikeabossTM forum member

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    Agreed, I've found most premature failures to present as internal shorts, and, when i researched replacement batteries a few years ago it seemed like Walmart had the most reliable manufacturer stocking their shelves.

    In any event, I'd shifted back to flooded with a good track record and good (4yr) warranty. Replacing a hundred dollar battery every 5-8 years is right up my alley.
     
  14. bambam 06

    bambam 06 Member

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  15. Juice

    Juice forum member

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    I second the battery tender for cars that sit for weeks without being started. These cars do have a minimal draw. Mine , after about two months of sitting, the battery may not have enough ooomph left to start.
    I use the Batrery Tender, 1.25A.
     
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  16. Pentalab

    Pentalab forum member

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    Mine went dead after not using the car for a month. Wouldn't start in -8.5 deg C outside temps. But the headlights, doorsill plates, map lights, radio, etc, all work just fine. There is a parasitic draw on the battery with the built in ignition immobilizer etc, on these cars. They need to be started at least every 2 weeks. For long term storage, they need a battery tender. That, or remove the battery, put it in the heated basement, with a battery tender on it. I don't have a garage, so it sits outside all year round.

    What ever you do, DON'T let your local dealer do a ..'battery test'. They essentially lay a dead short across the battery, with a clamp on dc ammeter. Trying to pull 540 amps out of a battery will fuck it up in short order. The start motor doesn't draw anywhere near that much current. I switched to mobil-1 0W-30 100% synthetic oil last year. (they also make 0W-20....and also 0W-40). With a good battery, and low outside temps, eng starts asap. That's good oil. Any block heater can be tossed. A few years ago, local dealer had block heater's on all new GTD-500 cars. This town is the last place that would require a block heater. Only a few days of the year where it hits freezing.
     
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