Hello

There is a very large class of people that own 65/66 Mustangs that, as far as I can tell, anyway, have been, for the most part, ignored entirely. They don't really want that 100 pt. show car that is so nice and was soooo expensive that they're afraid to drive it, they also don't want to make their car capable of achieving warp factor three. They just want this car that they dearly love to be able to cruise around smoothly and reliably, without having it dump them out on the side of the road or have it start making weird noises or belching out big clouds of funky-smelling smoke. And I think, truth be told, that this is by far the largest class of Mustang owners. They take their car to some technician when what they actually need is a mechanic, and this, frequently, does not work out very well at all for the owner. They don't want to re-engineer the entire car, they just want someone to fix what broke. These are the people that I am trying help out with this blog. Some problems require a little bit of back and forth, as in, "Try this." "I tried that and it didn't change anything."
" Oh. well, you probably need to try that." " I tried that and it helped, but it still isn't quite right." "Now you need to try this...." If you go to http://www.allfordmustangs.com/ and then go to the classics forums, you will be able to do that with a pretty hefty gathering of some very knowledgeable people that also happen to be very friendly. None of that ridiculous one-upmanship, no flaming or abuse, none of that stuff. Just good, solid advice from people that know what they are talking about.

Wednesday, April 2, 2008

Mustang Alternator and charging system 1965 and 1966





This is a system which seems to be a prolific source of confusion and despair for people, but it is actually quite simple, once you understand it. For all practical purposes, the only thing that your battery is supposed to do is supply power to start your car. After the car starts, all of the lights and gauges, and the motor itself, is powered by the alternator. The alternator also makes sure that the battery is fully charged for the next time you want to start your car. The alternator generates power and sends that out into the cars electrical system. This system, like all other electrical systems, can't just push power out into the void. The power also has to have a way to get back to where it started from, or, a ground. That's why they call them electrical circuits. The power has to take the entire tour. You have a black wire with a yellow stripe coming off of the alternator post marked ' Bat' that goes to the hot side of the starter solenoid. This is the same post that your positive battery cable goes to from the battery. You have a black wire with a red stripe that is attached to the post on the back of the alternator marked 'Grd'. This is, that's right, the ground. This is basically one wire with three ends. One end is attached to the alternator, one end is attached to the engine block on the same bolt that the negative battery cable is attached to, and the third end goes through the headlight harness and is attached to the radiator core support with one of the screws that holds the voltage regulator onto the car. You have a white wire that is attached to the back of the alternator on the post marked 'Fld. This wire goes over to the voltage regulator and is going into the terminal marked F on the side of the voltage regulator. It should be the terminal on the bottom with the voltage regulator mounted on the car with the plug thingy on the driver's side. There will be a yellow wire that goes from the voltage regulator terminal marked 'A' over to the hot side of the starter solenoid and that's all that there is for the actual functioning of the alternator itself. The alternator generates nearly 15V, it goes to the voltage regulator and gets knocked down to 12V, comes back and goes into the electrical system of the car. This part of the system is the same, whether you have an alternator light or an ammeter gauge. The differences between the two systems are all in the way that the charge indicator tells you what's happening with the system.

The charge indicator light works like this. There is a white wire with a black stripe attached to the post on the back of the alternator marked 'Sta'. That wire goes to the voltage regulator and then winds it's way to the charge indicator light and miraculously turns green with a red stripe along the way. There is another wire that is black with a green stripe that jumps off of the red wire with a green stripe that comes from the ignition switch and then goes to the charge indicator light. The light will have two wires coming out of the back of it, one black with a green stripe from the ignition switch and one green with a red stripe coming from the voltage regulator. The two pictures of the back of an alternator show how the wires are supposed to be attached to the back of it. The one with three wires attached to it, without one attached to the stator post is for a car with an ammeter gauge, and, the one with four wires attached to it is four a car with the charge indicator light.

The ammeter gauge works in one of two ways. On a 66 model car, it will have a red wire that goes out to the hot side of the starter solenoid, and a yellow wire that splices into the black wire with a yellow stripe that also goes to the hot side of the starter solenoid.
On a 65 model car that came with either the GT package ( performance/image option) or the pony interior ( Interior Decor Group) the ammeter gauge doesn't actually have any wires attached to it. It has that big black wire with the yellow stripe passing through a metal loop which is attached to the back of the ammeter gauge without actually touching anything. If I didn't have any understanding at all about automotive electrical systems and was asked to pick which one of these two systems normally doesn't work, the 65 system is the one that I would pick, since there aren't any wires attached to the gauge. But, I would be wrong. The 65 ammeter gauges almost always still work forty plus years later, and the 66 ammeter gauges, more often than not, didn't work brand new. There is nothing strange about your 66 ammeter gauge not working. It's nothing personal. They treat everyone like that.

20 comments:

devin8the8dude said...

Interesting site--when I unhooked the alternator harness, the ground wires were burnt and the insulation was off. concerned if it was wired wrong. white wire to field on alt. black/red stripe to grnd on alt. white /black stripe to stator on alt. big black /yellow stripe to batt. on alt. yellow from batt. on alt through firewall, possibly to gauges.

Mark S. said...

Veronica,

Thanks for this great blog on mustangs. You've provided info that has already helped me immensely in working on my '65 A code convertible. Specifically, your charging system description explained exactly what wiring set up I had, and what I should have.

Lots of little projects to complete like restoring under dash and door courtesy lights, glove box lights and proper horn hook ups. The previous owner disconnected the horns from the steering column for some reason, and routed them through the wiper washer switch (the washer bag, pump and related wiring are all now gone ..... of course.

Someone did a restoration, but not a great one. Many little things have been changed, altered or left out. I'm in the process of putting it back together to create a reliable (sunny and balmy weather) daily driver. This blog is now one of my reference points for going forward.

Thanks again,

Mark S.

Veronica said...

Thank you. I'm glad to hear that this has helped you out. If there is something that I haven't touched on yet that would help you, please feel free to ask.

Brent Warner said...

Hi Veronica,

Thanks again for this blog as it is very helpful! I have a '66 Mustang with stock wiring and ammeter. I would like to add the '65 style alternator warning light in addition to the ammeter.

Do you have any suggestions on wiring something like this?

Thanks,
Brent

Veronica said...

Thank you. That is very kind of you. As far as wiring the light goes, it would be a pretty straight-forward procedure. You would need to run one wire that's spliced into the red/green wire coming off of the ignition switch and another wire from the terminal on the voltage regulator marked 'S', and those two wires would go to the appropriate type of bulb socket. As far as where or how to actually mount that bulb socket, I really don't have any idea of how to go about that and have it look like something that's supposed to be that way.

benjie1458 said...

Hi Veronica,
I've been working on my son's '65 mustang coupe slowly but surely as a project car and been using your blogs as my primary source of info. Today, I remove the instrument cluster and the ignition switch to install a direct 12v power source wire to the newly installed DUI via the ignition switch and I noticed a somewhat soft unconnected black wire under the dash and traced it to one of the main harness and is joined by yellow/black wire and comes out to the engine bay as green/red and goes to the voltage regulator. I would like to know where this black wire should be connected to. Also, for information, I am disconnecting the red/green wire from the ignition switch which is connected to a resistor pink wire that is no longer needed and will replace it with the direct 12v wire for the new ignition system. Any insights, info or suggestions will be much appreciated.
Thanks
Ben

Veronica said...

It sounds like you are describing the charge indicator (idiot) light. Did this car come with the warning lights and the Falcon style speedo, or the 5 gauge cluster with the round speedo, like a 66?

benjie1458 said...

First of all, Thanks for the reply. To my knowledge I think it has the '65 original,typical style instrument cluster with 2 round gauges on either side and yes, it's somewhat related to the charge indicator light. The green with red stripe from the voltage regulator goes into the wiring harness thru the firewall and as I mentioned before, comes in as 2 wires-yellow with black and stripe (instead of green with red stripe) and black. The yellow and black stripe is connected to the back of the charge indicator light along with the black with green stripe wire. It is exactly as you described on this blog but instead of green with red stripe it's yellow with black stripe. There is no mention about this extra black wire even the '65 wiring diagram. I'm a little bit puzzled but I know you're on my side. Thanks.

Veronica said...

Is there a chance that this black wire is actually black with a dark green stripe? If yes, could you count how many fuses are in the fuse box? If there are six fuses, instead of just five, and one of them is marked turn signals, then you have the main underdash harness of a car that originally came with a generator instead of an alternator. If that is the case, there are some major differences in the way that everything is wired.

benjie1458 said...

There is a possibility that this black wire had a stripe but I asked 3 other friends and they all said it's black like a resistor wire with no markings. Also, there are only five fuses in the fuse box.

Veronica said...

That's odd. Is there any way that you could email e a couple of pictures of this stuff? The only black wire near the charge indicator light is the ground wire that goes from the attaching screw of the instrument cluster voltage regulator ove to the bracing behind the dash, and, obviously, it isn't tied into anything that's hot.

Veronica said...

Ford did not put that wire in the car. In the picture, it looks like the black/yellow wire ends and that black wire picks up where the black/yellow terminates at that funky looking crimp connector. What that black/yellow wire is supposed to do is come through the firewall and split into three wires. One of them is black/yellow, which foes to the emergency flasher and courtesy light circuits at the fuse box. One is yellow, and goes to the ignition switch, and the other is black/orange, and goes to the headlight switch. If the black/yellow wire does indeed end where that black wire starts, I would check and see which, if any, of those three places, ignition switch, headlight switch and courtesy light circuit where getting power.

If that black wire is just crimped in and piggy-backing the black/yellow wire, that was something that somebody did to get constant power to some component, like maybe a radio, that the car might or might not still have. I would also hook up the battery and see if that wire is hot all of the time. Let me know what you find out about what works and what doesn't, along with whether or not that wire is hot all of the time.

benjie1458 said...

Upon sorting all the wires behind the instrument cluster, that black wire is clearly not piggy-backing or crimped in to any other wires. So I hook up the battery to see if that wire is hot all the time like you suggested. First, I used the light tester and showed very dim lights during the test so I switched to the voltage tester and definitely showed very limited voltage of 3.4 when the key is on ACC and ON position. It seems to me like it could be a resistor wire for something and only allowing certain amount of power to go through. Any idea?

Veronica said...

There is only one resistor wire that is supposed to be in your car, and that's the one that goes from the ignition switch to the coil. If the other end of that wire is coming out of the voltage regulator, that would explain why it's showing a little power. Since that's not the black/green wire that goes to the charge indicator light, I don't really know what to say about that. Does everything work like it's supposed to without having that wire hooked up to anything?

Steve said...

Veronica,
Thank you for the information you provide on your site. I have a 65 that I cannot get the alternator to charge on. When I purchased the car the wiring harness was in the trunk and had been cut in multiple places. I didn't want to spend the money on a new harness so I repaired it and installed it. The engine had been in a later mustang so the alternator on it was not the correct one for a 1965. I replaced it with the correct one but it still does not charge. I checked and I have it wired as you show on your site. When the key is on I have 12V to the stator connector. I tried jumping 12V to the field post once and the alternator started putting out 17 volts and I could hear it pull the engine down. But I was getting 17V to the battery as well. With the jumper removed the voltage from the alternator slowly decreased. This made me think that my voltage regulator might be bad so I replaced it. This made no difference. Thoughts or ideas?

Steve said...

Veronica,
Another note on my charging issues. you refer to the wires on the charge indicator bulb as being black/green and green/red. My indicator light wires are yellow/black and black/green. I have the Scott Drake wiring diagrams that I believe are just a copy of the original ford diagrams. The page that shows the instrument panel information shows the charge indicator light wires as yellow/black and black/green. The page labeled ignition, starting and charging shows the wires as green/red and black/green and it shows the black green one splicing into the starter right before the resistor wire. This just leaves me even more confused.
Thank You

Veronica said...

First let me apologize for taking so long to get back to you on this. As far as the wiring diagrams being a little different goes, there were several changes made to the wiring during the 65 model year, going from a car that has a generator, idiot lights, and a horn relay to a car with an alternator, gauges, no horn relay. No single diagram could sensibly incorporate all of these changes. The SD diagrams are merely copies of one of the Ford diagrams, but, there were several different ones to choose from.

As far as your charging issue goes, it sounds like your problem is with the wiring going from the alternator to the regulator, probably in that section of it that goes inside the frame rail that is underneath the radiator. All sorts of ugly things can happen to a wiring harness in an environment like that. I would start by checking the white wire going from the field post on the back of the alternator. If that is broken, corroded, or shorting itself out somehow down there, your car would do exactly what you are describing.

Texas mongrel said...

So, my car seems to have a combination of charge light/non-charge light wiring. I have traced the charge light wiring both ways (from ignition switch and to regulator) and everything checks out fine. However, the light never comes on. The white/black wire from the alternator is missing. I could add this wire but I don't know where it would go into the regulator. Right now the connection to the regulator has three wires, white to F, yellow to A and green-red to S. . I think the small alternator harness with the three prong connector is for a non-light application, it has black-yellow, white, and red-black wires only. How do I fix all this? Your blog is the only one I've found that's understandable, hope you can help!

Texas mongrel said...

I have a gauge harness but want to use a charge light. I have wired the light correctly but it doesn't come on. I think this is because the alternator stator wire is missing, the alternator hatness is for a gauge car. Can I add the white-black wire, and if so, where does it go into the regulator? Right now the regulator wiring has white going to F, yellow to A and green-red to S. Thanks!

The Herriguys said...

I have a parasitic power draw on my 1965 coupe. I have replaced the alternator, voltage regulator and starter solenoid. Upon using a test light, I get power to ALL posts on the back of the alternator even with the key off. I'm not certain what should have power and what should not when the key is off.