high output alternator options

The alternator in my 08 GT500 died. I had it repaired at a local shop I have used many times with no issue. It has new owners and although it did charge properly I went out the next morning and the car was DEAD. I know the Shaker stereos have caused some battery drain so I assumed that was the problem especially since the head unit was cycling repeatedly trying to load CD's even though it was fully loaded. Pulled the stereo and recharged the battery overnight. Next morning car fires up no warning lights or messages and `~14.3 on the meter at idle. Next morning its the same thing completely dead. OK intermittent internal prob with battery was all I could come up with (batt was less than 2 years old and its my driver so it doesn't sit in storage) replaced the battery and once again everything is good. Dead again the next morning. Pulled the battery and bench charged for ~24 hours. Reinstalled the battery and disconnected the alternators connections. Next day all is well but I'm spooked. Repair shop wont do shit, I mean nothin'. Ordered an alternator from J2 Fab talked to them about shipping etc... on Friday and they would ship Monday. Apparently the owners wife has some new health issue and J2 went radio silent. Waited weeks but still nothing from them. Called mechman and left 2 messages in 2 days and no response. Lethal doesn't have anything in stock . I'm a little leery of PA as some people love em and some hate em. I havent dug in to the wiring changes that a Nations alt would require. Any thoughts or recommendations? Car is currently holding charge just fine and its been parked for weeks I'm confident the alt is the issue as the car maintains charge and I start it once a week just to check.

Does the truck alternator fit in these cars? They are usually higher output. I used to do that in the fbody cars, toss in a gm truck alternator, worked much better and you could just shoe-horn one in.

I'm not sure what would interchange but I'll look into it. I'm waving $100 bills around but I can't get an alternator. I'm still struggling with that . I have a spare for my Super Duty so Ill start there. Thx

OKSnake08 said:

I'm not sure what would interchange but I'll look into it. I'm waving $100 bills around but I can't get an alternator. I'm still struggling with that . I have a spare for my Super Duty so Ill start there. Thx

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Good luck, keep us posted. FWIW I haven’t needed to change an alternator in any of the S197 cars I have had (09 GT 500, 14 GT)… plenty of AC compressors though , hate that stupid ****ing stretchy belt on the coyotes..

I read it twice but might be missing something. It fires up fine and you read good voltage but the next morning the battery is dead. Why do you think it's the alt then?

Ok I see where you disconnected the alt then it was fine the next day. Crazy about Mechman, got my 370 from them. Mine went out and the fixed it and shipped it back within a week, great communication.



"Shorted positive diode will drain the battery with the key off and out."

"Bad voltage regulator in alt"

How to threads are for detailed how to threads, not help. Like how to add sprinkles to your ice cream. Moved.

I got lucky and Lethal had a couple J2fab alternators in stock and I got the next day. I would hit up some car audio groups and go that rout. J&S, Singer, Brand X, US Alternators, ect

Sorry if I posted this in the wrong forum. I know it was long but wanted to skip the “did you” questions. I never would have thought to go down the higher end stereo angle. So I’ll dig around there. I’ve been concerned about the car in the long term since PCM’s are virtually unobtainable and this “can I not have a junky alternator “ isn’t helping.
I was hoping Lethal would have one in stock. They were,as always, helpful and even went and checked it was there. Tried to bill it and it said they didn’t have any. Turns out a crank support had been stocked in the wrong location but at least they double checked and avoided another problem.

The torture never stops. Replaced the alternator with a 200 amp PA unit with their heavy positive cable in addition to the factory wiring and all seemed well. Battery 12.6-12.9 key off,14.4-14.7 at idle I did not drive it but put it under full electrical load and it tested fine, I had the stereo replaced. I drove it 5-6 miles and made a couple of stops on my way home when I picked it up. It drove fine, everything worked no lights no issues. Sitting at a light about a mile from my house batt light and charging system warning come on. Battery showed 12.6 and 14.7 at idle with batt light and charging warning on. Checked connections at the alt everything is fine. Start the car the next day, no lights voltages show the same, so I try it several times over 3 days and the problem doesnt recur. I was going to drive some laps around the house and see if it was some kind of fluke. I started it rechecked batt voltage and charge voltage all fine no lights. Put it under full electrical load- lights,stereo,A/C, rear window defrost. Again no lights and voltages are fine. Figure I'd heat soak it so I let it idle for 10-15 minutes both lights come back on. Turned it off and rechecked batt voltage it's now 12.8. Restart the car lights are on again so I turned everything back on and watched the meter while it idled14.4-14.7. When the cooling fan cycled it would drop to 12.9 for a split second then rise to 13.xx for another split second get to 14.7 then another split second to 15.01 then drop right back to 14.7. My fear is its a pcm issue but its communicating with my X4 and there is no check engine light and the only code is P1000 OBD test code which will not clear. It shows the correct vin and displays the strategy so it doesn't seem to be the issue. The P1000 doesn't bother me since I've had other vehicles set the code with no issues or CE lights just like this one is doing. I have visually inspected the harness and I dont see any issue so I'm stumped. I guess my next stop is the dealer. Any thoughts are appreciated. Thanks

P1000 code is indicating that emission readiness monitors testing has not completed. If all of your emissions systems are intact and functional, they will complete after several drive cycles. Disconnecting your battery or performing a KAM reset will likely trigger P1000.

Datalog the event with your X4 so you can monitor what the PCM is seeing and when. One of my newly re-manufactured OEM alternators quit charging under WOT, and I would not have known it without datalogging.

This is my Opinion. I went through 3 stock ford Alternators. Unfortunately the 07/08 Shelbys GT500 Alternators were not made of high quality like the 2010 plus had. I ended up going with a Nation's Alternator. I can tell you 100% that I had no issues with that Alternator. The wiring upgrade is easy. You don't even need to replace your factory wiring. You add the upgraded wiring on top of the factory setup.

What I did was measure the lengths I needed and had a local Stereo shop make the cables for me.

You will have a negative Cable that comes off the Alt that I chose to mount to the frame of the car.

You will have an additional power wire go from the back of the Alt that will go to the fuse box same as the factory wire

You will have an additional power wire go from the fuse box to the battery.

You will have and Additional Negative cable from the battery to the body of the car of your choice.

It's Farley simple. The only couple if things I had to do was. Drill the hole bigger on the factory wire to the Nation's alt as the stud was thicker than factory. I also had to get a longer bolt for the fuse box since you are attaching 2 additional cables too it.