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1967 Ford Mustang Coupe
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Discussion Starter #1
Hey everyone. As you can see by my subject I'm having trouble getting my battery to charge. I have a 67 Mustang.

When the problem first happened our mechanic told us to replace the battery so we did. And that worked fine for a little while. But after a couple of months the battery stopped charging. The place we bought it from was kind enough to replace it but the same thing happened again.
At that point my dad decided it must have actually been the alternator that was the problem so we replaced that. That worked for a short time as well but we noticed the car needed to be jumped a few times. We can take the battery out and charge it and it will stayed charged for about a month but that's just a hassel to be doing all the time.

Does anyone have any ideas on what the problem can be? The wire that connects the alternator to the battery looks like it is completely covered in electrical tape. Would just replacing that wire fix it?
 

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1969 Mach 1 351 Black Jade
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21 Posts
Def take the electrical tape off and see if there is a bad or corroded connection first.
 

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11,772 Posts
These old Mustangs had a separate voltage regulator that could also be defective. You have to check the entire system- battery, alternator, regulator and wiring.
 

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How often do you drive it? How long does it sit? Do you have an aftermarket digital radio? Do you believe the problem is the battery isn't charging or that it is going flat while sitting?
 

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My guess would be voltage regulator. You can have it tested along with the alternator and you should be able to figure it out. I had a similar problem a month ago. turned out to be my alternator as my battery wasn't charging either. I took my new motorcraft electric voltage regulator and older rebuilt alternator to the local parts store and they quickly determined it was the alternator.
 

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To see if your voltage regulator is working, the battery will measure around 12-13v when sitting. When the car is started and revved a little, the battery voltage should go to just over 14v. If the voltage reads higher, like 17-18v then the regulator is bad and it will eventually kill the battery. If not 14+v when running then the battery isnt charging from the alternator.

If the car sits without being driven, it may be a good idea to connect one of those battery disconnects to the neg terminal to avoid something drawing current and running the battery down.
 

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I have 2 stock classics (a 66 Mustang and a 67 Cougar) that sit idle for several weeks at a time. To keep the battery up, I remove the negative battery terminal. No extra parts to buy and just a minute to run a battery post cleaner in the connections before firing up the cars.
 

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To see if your voltage regulator is working, the battery will measure around 12-13v when sitting. When the car is started and revved a little, the battery voltage should go to just over 14v. If the voltage reads higher, like 17-18v then the regulator is bad and it will eventually kill the battery. If not 14+v when running then the battery isnt charging from the alternator.
^^^^ Do this first. Simple.
 

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If something isn't draining the battery they will stay up for a LOOONG time. My 65 200 CI. with no aftermarket radio or anything can sit all winter, and still spin the engine over like new in the spring. But I do put a charger on it once in the middle of the winter. Now my 64 ranchero I put a disconnect on because it has a slow drain. And of course the 98 mustang I put a charger on about once a month if I don't drive it much.
 

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1967 Ford Mustang Coupe
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Discussion Starter #11
I'm told the voltage regulator is brand new.
The previous owner did put in a cd player with flashy lights and new speakers.
We were driving it nearly every day. My dad used it as an everyday driver. He never drove very far with it and if he wasn't going anywhere he would run it for 10 minutes.
 

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I'm told the voltage regulator is brand new.
That doesn't guarantee anything. There's lots of cheap chinese crap parts for sale these days. If you don't have a voltmeter to measure the voltage drive the car to one of the major parts stores and let them test it for free.
 
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