05’ GT new battery

JC SSP

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Hi Team,

My GT did not start at home the other night with no prior warning.

Next day did a battery check with voltage meter and completely dead. Went to neighborhood Auto Zone and got a free battery under warranty.

Check the care idling 13.53V with no load and then A/C on high, headlights on, emergency flashers, wipers on high, etc. and still got 13.58V. I think I am OK but read that I should be at 14V. My Audi and new Hemi Durango are always at 14.2V.

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moooosestang

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My car is usually 14.3v all the time when running, but i have an aftermarket alternator from PA performance. Is the alternator stock? the stock alternators are a known issue on these cars. the diodes go bad and leak AC current into the system causing all sorts of gremlins. I would stay far away from the box store alternators as well. The PA is expensive, but mines been good going on 13 years now. Not a ton of miles on it, but plenty of heat cycles which is what kills batteries and alternators.
 

JC SSP

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It has a custom 200amp alternator that’s about two years old. Maybe 6,000 total miles.
 

DieHarder

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Alternator output should be above 14v. Honestly, your cabling doesn't look all that good. Appears you have a bit of copper oxidation going on. Do a couple of voltage drops with engine running (output of alternator to body of alternator; body of alternator to some point on the engine; body of alternator to passenger strut tower ground; etc. If you see voltage drops at various points on the engine (i.e. 1 - 2 volts) your grounds need work or you need new battery cables. I replaced mine and saw almost a 2v jump in voltage. Also added a ground (4 gauge) from an alternator mounting bolt back to the passenger strut tower. That ensures the alternator and the body grounds are at the same potential (absolute ground). Otherwise one ground (i.e. engine) can float relative to the body if the batt/ground cables have built up resistance over time due to oxidation/corrosion.
 

Ret

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When I upgraded to my 2012 Mustang GT, I took it for a test drive and to my mechanic before buying the car. It ran great and my mechanic stated despite how bad all the corrosion looked the battery was new and everything was working. I bought the car and ordered new cables (thinking the 4 to six foot kind). The new cable arrived and both myself and my mechanic thought the wrong part had been sent.

I had it replaced at a cost of $700.00. There couldn't have been more corrosion and embedded in a braded copper wiring as well. After I posted the photo below several members came on with solutions to the corrosion that cost 5 or 6 cents as I recall.
One involved sea water, the other a 2 or 3 cents worth of chemicals.

Unfortunately all this great advise came after I had spent the $700.00 and had replaced the cable. As you can see the cable isn't the typical cables we all grew up with. I don't know, what year this type cable went into Mustangs but my mechanic said several of the leads went to individual computers in the car. The only part of that cable that was bad was at the battery connection. The recommended sea water or chemical cleaning certainly would have been less expensive.Mustang wiring.jpg
 

DieHarder

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When I upgraded to my 2012 Mustang GT, I took it for a test drive and to my mechanic before buying the car. It ran great and my mechanic stated despite how bad all the corrosion looked the battery was new and everything was working. I bought the car and ordered new cables (thinking the 4 to six foot kind). The new cable arrived and both myself and my mechanic thought the wrong part had been sent.

I had it replaced at a cost of $700.00. There couldn't have been more corrosion and embedded in a braded copper wiring as well. After I posted the photo below several members came on with solutions to the corrosion that cost 5 or 6 cents as I recall.
One involved sea water, the other a 2 or 3 cents worth of chemicals.

Unfortunately all this great advise came after I had spent the $700.00 and had replaced the cable. As you can see the cable isn't the typical cables we all grew up with. I don't know, what year this type cable went into Mustangs but my mechanic said several of the leads went to individual computers in the car. The only part of that cable that was bad was at the battery connection. The recommended sea water or chemical cleaning certainly would have been less expensive.View attachment 92277

My god.

That's beyond highway robbery and the reason I do just about all of my own work. This is a simple plug-an-play affair that takes only a few of hours if you're taking your time. Understand paying someone else if you physically cannot do the install but what they charged you is obscene (I'm at a loss to fathom why that job would justify so much; replacing a harness isn't rocket science).

If you're ever unsure what is connected to what there are a few online manuals you can reference. Here's one: https://iihs.net/fsm/?d=0

and a detail link: https://iihs.net/fsm/?d=711&f=151 - Component Location Views.pdf
 

moooosestang

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When I upgraded to my 2012 Mustang GT, I took it for a test drive and to my mechanic before buying the car. It ran great and my mechanic stated despite how bad all the corrosion looked the battery was new and everything was working. I bought the car and ordered new cables (thinking the 4 to six foot kind). The new cable arrived and both myself and my mechanic thought the wrong part had been sent.

I had it replaced at a cost of $700.00. There couldn't have been more corrosion and embedded in a braded copper wiring as well. After I posted the photo below several members came on with solutions to the corrosion that cost 5 or 6 cents as I recall.
One involved sea water, the other a 2 or 3 cents worth of chemicals.

Unfortunately all this great advise came after I had spent the $700.00 and had replaced the cable. As you can see the cable isn't the typical cables we all grew up with. I don't know, what year this type cable went into Mustangs but my mechanic said several of the leads went to individual computers in the car. The only part of that cable that was bad was at the battery connection. The recommended sea water or chemical cleaning certainly would have been less expensive.View attachment 92277
vinegar and salt will clean all the corrosion off of copper in short order. For future reference.
 

Ret

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I agree terrible waste of money. My problem is I know my limits, I know how to drive a car, but my mechanical skill suck.
 

JC SSP

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A man has to know their limitations…

I will rebuild a motor but working on an automatic transmission is out of my level of proficiency.
 

Ret

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Yeah, here was a chance for me to learn to work on cars. My dad was a great mechanic and I should have been able to learn from him. But he also was an alcoholic with a terrible temper and violent. So you gave him a wide berth to stay out of his way. I think I posted the following before. When I bought my first car my dad said make sure you have good brakes, tires and full oil level. I had the car over a year before I found out you were supposed to change oil. I would check the oil level and add oil as needed.

So, I found a good mechanic and been going to him for 23 years.
 

DieHarder

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I have the same issues with my son. Can barely get him to check oil/water/power steering. If you don't have an interest in learning about cars then you don't have an interest. I started getting excited about cars when I bought my first "good" car. A 1968 Charger w/a 4-speed. God, how I wish I still had that car. Later I had a '74 Lotus Europa and after that a Maserati. You only learn when you brave the unknown. Much easier of course if you can rely on others (military autoshop) or better when you buy the shop manuals which I learned when I bought the Lotus and Maserati. Cars aren't really all that mysterious or difficult to understand and work on but age does slow one down. I'm up there as a senior these days and find it more difficult to crawl underneath a car for hours at a time. I can still do it if I need to but sore for the next few days.
 

Pentalab

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I measure 12.4 vdc with car sitting. And 14.75 vdc at idle....or any higher rpm. This is using a calibrated fluke 87 dvm. Next, switch the meter to read AC voltage. It should be zero, or minimal, like < 200 mv. If the AC voltage is reading more, then one or more diodes has failed shorted.... and you end up pumping raw AC into the battery....which will fry a battery in no time.
 

JC SSP

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Update.

I was doing my annual maintenance (oil, oil filter, fuel filter, lube etc) and cleaned up the terminals as best I could. Did another check and volts are doing slightly better. 14.1V at Idle and 13.9V at load (A/C, flashers, headlights on, etc.).

I am ok with this for now but will monitor as always.

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Pentalab

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You might want to try a different DVM. urs might be reading on the low side. What is the battery voltage with eng off...like say the next morning ?
I measure 12.5 vdc. And 14.75 vdc with eng on...and idling.
 

JC SSP

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Yeah my Craftsman one that I had for 30 years gave up the ghost so I got this one from HF.

I will get a new one and do a morning voltage test.
 

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