67 Barracuda alternator with 2 FLD connections

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Bobacuda

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The PO of this car and his junkyard parts are driving me nuts. He also played with the wiring.

The alt that came with the car has 2 FLD connections. Both had wires, but on this car, that doesn’t mean anything (about to go chase the wires through the harness). The rebuilt alts I see online, my 67 Plymouth shop manual and the Barracuda supplement wiring diagrams only show one FLD on the back of the alt... what is going on?

No numbers left on alt. Any idea if it should have one or two FLD connections (as seen in the photo). Is this normal?
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Which voltage regulator do you have? That determines how the alternator is connected. I think 70 and later is flat & low profile with a triangle connector and 69 back has the boxy looking mechanical one. Yours could have been swapped. Take a picture of it.
 
I attached a photo of the back. It is not a “square-back.”
 
BTW, the PO removed/eliminated the VR. Went from the alt to ballast resistor, via a wire cut from an extension cord.

car was not running when I bought it.
 
There's a way to ground the extra field terminal that you don't need...
 
You can’t use that alternator without a regulator. Number of wires hooked up to it doesn’t change that.

If the alternator is being used with two field wires you should have a regulator that looks like this.

Do you mean the PO eliminated the mechanical voltage regulator? That is what I did on mine and now have the one in the picture.

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No VR whatsoever. There are cut & non- color coded wires everywhere. Could not chase wires with ohm meter - gave up.

I bought new wiring from M&H. Time to pull it out Of the box and see what alt and VR it wants.
 
I did the same thing. Bought a M&H under hood harness. Worked out well. I bought the one already wired for electronic ignition and the two field wire alternator. Make sure you clean up the bulkhead connector good and grease it when you reassemble.
 
Pics of engine bay help a lot in your scenario. Smart move with buying M&H harness.
As mentioned above you need a regulator.
 
my 67 Plymouth shop manual and the Barracuda supplement wiring diagrams only show one FLD on the back of the alt... what is going on?
What is going is this. Sometimes its easier to pick up an alternator with two filed terminals and ground one of them. I've had to do that on several occasions.

Here's one
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What happened was this. In 1970 Chrysler implemented a solid state voltage regulator on all vehicles. At the time, the type of transistor needed to regulate the power feed to the rotor would have been more difficult (costly) to implement. At least thats the best we can figure. So instead they made a regulator that controlled the rotor's ground.

In a '67 the regulator controls the current feeding the rotor (aka field).
Field is short for Electro-magnetic field. Electrical current through rotor's windings makes a magnetic field.
Alternators create electric power by spinning that magnetic field and inducing current in fixed set of wire windings. The regulator controls how strong the magnetic field becomes by controlling flow into the rotor.
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Internally, a set of points moves between three positions.
1. No flow
2. Flow through resistors
3. Direct flow.
 
It is going into a 67 Barracuda Formula S convertible, 318 (plain Jane - PO blew up the 273 and inserted a 318) automatic, no AC. Nice daily driver ( I hope). No big stereo or additional lights.
 
It is going into a 67 Barracuda Formula S convertible, 318 (plain Jane - PO blew up the 273 and inserted a 318) automatic, no AC. Nice daily driver ( I hope). No big stereo or additional lights.
IMO there is no real advantage to converting to the '70 up alternator wiring.
You can buy a stock looking regulator with either electromechanical or transistorized internals.
 
IMO there is no real advantage to converting to the '70 up alternator wiring.
You can buy a stock looking regulator with either electromechanical or transistorized internals.

The only reason I upgraded to the newer regulator was because that was the configuration of the M&H harness that was pre wired for electronic ignition.
 
The only reason I upgraded to the newer regulator was because that was the configuration of the M&H harness that was pre wired for electronic ignition.
When using the electronic ignition it was always considered to be more reliable to use the transistorized regulator.
Eventually there was a transistorized regulator available from Mopar Performance that could be used with the earlier wiring.
And now, its all a crapshoot as far as quality of components and assembly.
If I was running a points distributor, I'd almost certainly go with a mechanical regulator if I found an old one in good condition.
I've got a Standard equivalent of the MP regulator on my '67 right now. And I have FBO's factory looking transistorized one from their ebay store. It's my backup.
 
It is going into a 67 Barracuda Formula S convertible, 318 (plain Jane - PO blew up the 273 and inserted a 318) automatic, no AC. Nice daily driver ( I hope). No big stereo or additional lights.


Please read carefully what is being posted here. Regardless of "round back" or "square back" a round back can have ONE or TWO field connections. The two is known as ISOLATED FIELD and was used starting in '70 but!!!........

There are TWO regulators. The "up through 69" regulator hooks to switched ignition power and the field wire and you ground it. Done That is used with a single terminal field alternator. If you have TWO simply ground the remaining field

The flat looking electronic used in 70/ later wires exactly the same EXCEPT the alternator must have two field connections, and the last field terminal is wired to switched ignition power.

So the "flat" 70/ later gets ground, ignition power, wire to one field, and second field goes to switched power

The early 69/ earlier regulator gets ground, ignition power, and wire to the only field connection

Simple
 
What amps would my 67 need? I do not have an existing VR to compare to and there are no identifying marks on the alternator.
 
What amps would my 67 need? I do not have an existing VR to compare to and there are no identifying marks on the alternator.
Pretty much any standard alternator will work.
There are hardly any electric loads other than headlights, heater fan and wipers.
If they are all running, together they will draw around 20 to 25 amps at 14 Volts
Ignition and field will draw about 5 amps.

Not that the amp 'ratings' of an parts store alternator are anything to put much meaning into.
Just posted about this recently. here: Alternator?

The part number probably got sandblasted off during one or more rebuilds.
If its anywhere, its here. But as its rebuild, who knows if the original rotor and stator are in it?
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The test specs in the '67 service manual are not the rating.

This is snip from a '69 or '70 FSM but the point is that its a maximum load test at 1250 engine rpm, 15 Volts.
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We can sometimes relate the test specs to the Chrysler alternator 'rating' by looking for the same description in other books.
This is from the dealer data book.
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source: The 1970 Hamtramck Registry Library Page (1965 - 1969)

Sometimes there is a part number for the ratings, such as service bulletin 66-78, which can be found here:
The 1970 Hamtramck Registry "1966 TSBs and Related Material Index" Page

If you got to get one from a parts store, see what they have. If they call it a 40 or 50 or 60, any one of them is probably fine. I wouldn't take one that was 'rated' over 60amps though.

I'll add that I had quite a few slant six cars and above idle speed the alternators always were able to power lights and wipers even with the heater fan on.
 
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This is the breakdown of current measured with a clamp meter on the alternator output of my Grand Wagoneer.

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That has a Duraspark ignition which uses a little more current than a points ignitions.
It has a 12SI alternator whose field is internally powered, so that may not be getting measured on the output wire.
Headlights were H4s which draw more power than the 6012 sealed beams a '67 came with.
This Jeep has about the same instrument lights but also side marker lamps which '67s don't have.
 
Hey Mattax, what kind of clamp meter do you have that measures DC current?
 
For that I used Innova's Current Clamp 3347 with their Automotive Multimeter 334A.
I should have some pics..well somewhere. :rolleyes:
After figuring it out, it works pretty well.
Since then I bought a VAT-40, but I'd still use the Innova with its clamp for measuring in the 5 - 30 amp range.
 
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Thanks Mattax. That Innova is pretty cool and reasonably priced. I have had an AC clamp meter for years, but have never had a DC one. Gonna have to get me one....
 
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