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New alternator not charging battery.

574 Views 14 Replies 5 Participants Last post by  bluecguy19.jr
So I have a 2006 mustang GT the original alternator went out about 3 years ago. Probably had about 150,000 mi. Put in a TYC with a new battery and it died on the way home from work. Suspecting that this aftermarket alternator crapped out I got to rebuilt motorcraft and lo and behold it's not charging the battery either!? Some people have said replace the power wire from the alternator to the battery, other people said your battery has a short get a new battery and somebody else said check the grounding strap on the passenger side of the engine block to the frame!? Not sure what step to take but I'm thinking of taking the battery out of my ranger this weekend and see if it'll start and charge? Any suggestions would be very much appreciated!
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I would pull out my handy volt meter and start checking voltage.
I did that was the first thing I did was put the multimeter on the battery to check the new alternator at what it was charging at and I couldn't believe my eyes! It shot up when the car started and then just started dropping and I shut the car off before it died but it was about to die.
I would inspect all grounds and cables.
On this generation of car I believe that the PCM is what's responsible for maintaining the battery charge and adjusting the voltage from the alternator.
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Yeah I put the old alternator back in and tried that with the new battery and the voltage went up higher then it started going back down again and hovered a little bit over 12 again so I'm going to have the new alternator checked and if it's good I'm going to put the new alternator back in again with the new battery and take it to the shop and have them figure it out because I'm not going to crawl underneath an all-around that thing checking every ground wire and I'm not capable of troubleshooting the PCM but I appreciate the response.
It sounds like you just got 2 bad alternators with the newer one probably being worse. Rebuilt electrical parts are incredibly unreliable and many times alternators and starters will be defective when rebuilt because of low quality/cheap parts and cheap labor. These were the 2 most returned parts for being defective when I worked at an auto parts store long ago. Even if they work initially then they usually don't last for long anyway.
It's always best to have your original alternator rebuilt by a local electric motor shop that certainly won't be using low quality parts since they don't want angry customers coming back to them. This is what I recommend that you do.
The other option is buying a brand new one from a reliable company like PA Performance. They have a known excellent reputation and use the highest quality parts like an electric motor shop would.
I'm going to take the rebuilt motorcraft either to allied or carquest and have them check it and make sure this new rebuilt is working if not allied's going to have to give me another one either way if the one I have is indeed working I'll put it back in or get another one and put that in and then check the voltage again and if it's low still it's going to go to the shop.
Your old one only charging at just above 12v is not working. You should generally have no less than 13.5v at any time coming from the alternator. 12 something volts is not going to keep up with the electrical demand and the battery will decharge. Your battery as it sits with the engine off should have at least 12.5v but the alternator has to be pumping out well more than that to keep it charged at that level.
The new one is also apparently defective if it's decharging the battery with no other abnormal existing battery drain. You should have them test it so they can see that it's also a defect but I suggest to just return the defective rebuilt Motorcraft and get your $ back and then take your old one to your local electric motor rebuilder. Even if the auto parts store swaps your rebuilt out for another and you're lucky enough to get a working one then you have no idea how long it will last. It may be only a month or a year or a couple years if you're lucky. Remember that you only got 3 years from the one that you replaced a while back and that's about the max for an average auto parts store rebuilt one.
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Wow I really appreciate that advice. It's hard to believe though that the new one I bought is also bad I thought they test these before they put them on the shelf? Anyway I will take it today after work and have them test it and see what they say. I don't know if they'll give me my money back on electrical parts? But yeah I was thinking the same thing It's got to be at least 13-5 13-8. What's your opinion on this alternator wire people are telling me about? Summer saying that there's the fusible link in there that will go bad and still let current go through but won't let it charge properly and others are saying there is no fusible link it's just a wire. Allied told me it's a wire no fusible link but then again they're the ones who sold me that rebuilt motorcraft. Lol
Something I wanted to point out as well. Check to make sure your multimeter is correct. I was diagnosing a voltage issues with my 07 Impala and I was shocked to see with a new alternator I was pushing like 15.4v with it running. I borrowed a multimeter from work and it was around 14.1v so my meter was ready way high. Prior to that, I was diagnosing an HVAC issue in my house and I noticed both legs of power were running like 134v each lol.
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If it's a defect then they have no choice but to give you your $ back. You can simply call your bank and dispute it if you paid with a card and your $ will be returned to you.
Wow I really appreciate that advice. It's hard to believe though that the new one I bought is also bad I thought they test these before they put them on the shelf? Anyway I will take it today after work and have them test it and see what they say. I don't know if they'll give me my money back on electrical parts? But yeah I was thinking the same thing It's got to be at least 13-5 13-8.
What's your opinion on this alternator wire people are telling me about? Summer saying that there's the fusible link in there that will go bad and still let current go through but won't let it charge properly and others are saying there is no fusible link it's just a wire. Allied told me it's a wire no fusible link but then again they're the ones who sold me that rebuilt motorcraft. Lol
What alternator wire?
Do you mean the PCM control circuit wiring to the alternator? Scan the car for trouble codes to see if there's an issue in that wiring. The PCM monitors any electrical anomalies within that circuit and P0620-P0623 and P0625-P0626 will reflect an issue within the control circuit wiring. If you've disconnected the battery recently codes will be erased but most or all alternator control circuit codes should register immediately once the ignition is turned to on. Check the condition of all the wires and connectors coming off the alternator.
There's another thread going on right now with a similar problem to yours with the same year car: (207) P0622 Code 06 GT 4.6L | Ford Mustang Forum (allfordmustangs.com)
I'm not aware of any fusible link between the alternator and starter solenoid/battery. They were used in older vehicles but were always a cause for confusion and were a total pita. I'm pretty sure most or probably all fusible links were done away with in more modern cars.
However, there's a fuse in the engine compartment fuse box for the alternator. That's typically either completely blown or it's not 99.9% of the time. If it were blown then you would be getting no voltage at all from the alternator. Your owner's manual will tell you which it is.
My 1992 Ford mustang did that I put 3 alternator a new ecm it turned out it need a ground and I ain't had no more problems so what somebody said above about the ground do it I believe that's your problem solve.

Also I put a ecm like I said do what somebody posted above about the ground I believe you will have no problem good luck
So I have a 2006 mustang GT the original alternator went out about 3 years ago.
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So what happened to your grounding strap did it break? Or did somebody vandalize your car and just get underneath there and cut it or was it just a bad connection you needed to clean?
My 1992 Ford mustang did that I put 3 alternator a new ecm it turned out it need a ground and I ain't had no more problems so what somebody said above about the ground do it I believe that's your problem

My 1992 for mustang gt did the same thing I put 3 alternator it and batterys it turned out it was a ground do what somebody said above I believe your problems solve
In my first post I mentioned checking your cables and this should be the first thing to check.
Sometimes corrosion simply creeps between the connection between a ground cable and its mounting points(usually the block and/or sometimes the chassis). Other times a clean mounting point was never actually achieved from the factory and the ground barely got by until one day it just doesn't make enough contact to do its job from paint, unnoticed corrosion or contaminate, loose or just poor contacting fastener, etc.
I've mentioned this a few times before and I think I once even posted the link to the video but there was 2005-10 v6 owner that had a no start condition and it turned out to be a combination of one of the clutch pedal switches and the ground cable on the block. The shop simply loosened and tightened the ground cable mounting bolt and voila ground was reestablished. After being frustrated that the car wouldn't start someone had pushed in the clutch pedal way too far and over ratcheted the clutch switch but the ground cable was the original and main issue.
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Thanks for the reply bud. I will definitely check out the grounds. I've already started to do a little more research and it turns out there's three grounds on these cars, one on the driver side firewall to the driver side head. Then there's another on the passenger side strut tower and then the one that's a real PITA they say, passenger side from the engine block to the frame. With all those grounds it's hard to believe The car would lose ground but apparently with all these problems popping up they do!?
In my first post I mentioned checking your cables and this should be the first thing to check.
Sometimes corrosion simply creeps between the connection between a ground cable and its mounting points(usually the block and/or sometimes the chassis). Other times a clean mounting point was never actually achieved from the factory and the ground barely got by until one day it just doesn't make enough contact to do its job from paint, unnoticed corrosion or contaminate, loose or just poor contacting fastener, etc.
I've mentioned this a few times before and I think I once even posted the link to the video but there was 2005-10 v6 owner that had a no start condition and it turned out to be a combination of one of the clutch pedal switches and the ground cable on the block. The shop simply loosened and tightened the ground cable mounting bolt and voila ground was reestablished. After being frustrated that the car wouldn't start someone had pushed in the clutch pedal way too far and over ratcheted the clutch switch but the ground cable was the original and main issue.
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