1940 Ford 6/12 Volt Charging System

i would check the output of the alternator directly coming out of it

I no longer remember when and how generators were changed (I had a 46 Ford), but do you have the old style generator where the third brush had to be moved to function as a crude regulator? You've also got a couple of folks about an hour south of you (Car and Carriage Museum at Luray) who probably know as much about old cars and their problems as anybody on the east coast, if you can find them and get them to help you.

Did that once upon a time.....pulley size on generator was wrong...not moving fast enough to maintain charge ..also note that 13.5 volts does not mean that amps are acceptible....

Yeahp, I would just turn on the engine and measure with any voltmeter the battery terminals. It must read those 13,5V first of all. If so, take a look at your battery. If not, there may be something wrong with the gen, or any short/current leak somewhere.

From 53 on Ford generators were internal ground design. In order to test the generator, while it is still mounted to the car, follow along.

• Check for tight connections on the generator, regulator and battery.
• Check for battery voltage at the regulator at the terminal marked BATT. It should match the battery voltage, or your wiring is wrong between them.
• Start the car, and be very careful. Connect an ammeter between the battery positive post and the terminal on the generator marked A, or ARM. At the same time, connect a wire from the A, or ARM terminal of the generator th the F, or FIELD terminal on the generator. If the amperage matches the rated output, the regulator is bad, and needs repair, or replacement. If you are reading battery voltage while running this test, the voltage becomes unregulated. If you rev the engine, the voltage will go very high. Don't burn out anything.

In case you need to know, the A, or ARM terminal on the generator connects to the A, or ARM on the regulator. It might be labeled GEN.

The F, or FIELD terminal on the generator connects to the similar terminal on the regulator. The remaining terminal on the regulator leads to the battery, and it is marked BATT.

If you need to chase parts, all Fords are 12 volt from 58 and later. T-birds are 12 volt from 56 and later. Good luck. What motor is in your car?

Hello Guest

Couple of points.

What's the relevance of the disconnect switch on the battery? Presumably this is closed during normal running.

Where is the 13.5 volts measured? At generator output terminal, or regulator output, or battery?

What type of regulator, the older 2-bobbin or later 3-bobbin type? If it's in keeping with the age of the car, likely to be 2-bobbin.

Assuming it's 2-bobbin, the 2^nd bobbin regulates both voltage and current. To adjust the setting, need to disconnect the regulator output from the battery, so there is no output current. Feed ignition and accessories direct from the battery to keep the engine running. Voltage is then adjusted to quite a high value, 16.5 - 17.5 volt (measured at regulator output terminal). In normal running the output current also affects the regulator coil so brings the volts down, even when the battery is well charged so there is only a trickle charge. 13.5 volts is well down and increasing it might cure the problem.

Cheers.......Codey

Carl,

I've removed your email address and phone number from your post. That's the kind of stuff that spiders and spammers on a "phishing" expedition would love to get a hold off.

If you register with CR4, you'll find that you can be notified automatically whenever someone responds to your question. There's a private messaging system, too. Hope you'll register with us (it's free) and keep coming back.

Moose

Aside from putting an inductive meter on the cable and measuring current, I can't offer any help here simply because it's been so many years since I was called upon to fix such things,

What I am a bit perplexed by is why you didn't simply substitute a more efficient alternator than go to the expense and trouble of modifying a less than efficient generator.

Yes, I know, the purists will cringe at such a suggestion but since it's not likely you'll be putting up the car for sale at an auction of restored antique cars, an alternator would be the more effective solution.

No?

L.J.

I had a 1935 Ford with a 1938 V-8 85 flathead and converted it to 12 volt by putting an alternator in place of the generator. There are alternators with the regulator circuit built into them so it just drops in where the generator was. My Dad had to look twice to recognize what it was, and he owned the 35 before and after me.

Also remember to put an ignition resistor in line with the points to prevent pitting and burning up the points when converting to 12v. The alternative is to put an electronic ignition sensor in that works on 12 volts, www.pertronix.com as I recall should have ignition and coil.

I also took a mouse nest out of the radiator, which was causing over-heating in 2 or 3 miles, next I had to put in thermostats.

As far as I remember, that Ford had an external resistor with "4volt" ignition coil in a bakelite housing. It would be better to use a coil with a primery winding with a 1.5 to 1.6 Ohm resistance with a external resistor of about the same resistance. The combined resistance of the coil primery circuit should be between 3 and 4 Ohm.

To polarize an A-type generator [The field winding is internally connected to one of the brushes]: 1. Earth the F terminal, 2.Lift one of the brushes and slide a piece of paper between the brush and commutator, 3.Momentarily connect battery + to the generator A terminal.

Polarize B type [Field internally earthed] Just connect Battery+ to generator F momentarily.

It has happened that one of the field coils was fitted the wrong way round thus two magnets of the same[N or S] poles face each other and gen. will not charge!

Heh Guys...what ever happened to shorting the positive lead to the gen case to "polarize" THE GEN? ............WOUND FIELDS REQUIRE IT

I learned this in the mid thirties...standard practice when changing out/replacing either battery or gen.

DON'T FORGET TO ADD RESISTOR FOR THE POINTS IF YOU KEPT THE ORIGINAL

I am qualified.............83 birthday this week. Had several 36 to forty Fords

MR. GUY

Polarizing a generator is an important point. How soon we forget!!

Also keep account of the system polarity. Old Fords were 6 volt positive ground.

A couple of other points here...... 6 volt flathead Ford starters work fine on 12 volts. All you need to do is make sure the starter bendix is in good shape because it is handling more power and speed on 12 volt starts. How do I know this? Well, a close friend has a string of Bonneville and El Mirage roadster records with Ardun Flatheads, fuel and gas. He used stock Ford flathead starters on 12 volts exclusively for starting the unblown race motors. One was a 286 cubic inch Ardun alcohol motor with a 16:1 compression ratio that put out over 400 hp.

Another point -- Old Ford 6 volt instruments work fine on 12 volts. If you research the design of automotive electrical instruments of 60-70 years ago you will find they were designed with a very clever little bridge circuit that compared voltages. That way the inaccuracies that a simple resistive circuit would have as system voltage varied with engine speed and battery charging would be largely overcome. This didn't apply to the ammeter, which had a simple inductive coupling to a power wire.

When I converted my everyday driver 41 Ford pickup that I used for 9 years back in the 60's to 12 volt negative ground all I had to do was replace the regulator to match the engine, change bulbs, put a resistor on the heater fan wire and turn the ammeter wire 180 degrees. (the windshield wiper ran off vacuum and there was no radio) The 6 volt 51 Plymouth starter worked fine (on the stock 51 Chrysler V8-331 hemi), the original Ford instruments all were accurate although noticeably more responsive due to their internal dampening being designed for 6 volts and the 6 volt Ford horn worked great. I ran that Chrysler setup for 9 years including towing a car to and from New Jersey to Texas and the only real problems I had with it were in the transmission and rear axle department. That's another story..... and a bit off topic.

Ed Weldon

"Old Fords were 6 volt positive ground."

Boy is this string "generating" (sic!) memories amongst my cobwebs!

Polarizing the generator, 6 volt system, positive grounds. Wish I could upgrade body parts as easily!

Do any of you remember the reason for switching to negative grounds? I know the Brits still had it, at least as late as 1963. Did it have anything to do with galvanic reaction and corrosion?

L. J.

Mack trucks continued with positive ground way into the seventies.

Why did the manufacturers go to neg ground?

Claimed to have less rusting of bodywork.

Do anyone remember the gadget which ran from the battery to wired rubber strips stuck underbody on both sides of a car...claimed to negatively charge the body to prevent rusting? Did it help?

Two months ago I purchased two "static eliminators" from my local NAPA store. The truck that I installed them on has almost 8 feet of front overhang. The truck must routinely pass through an automated electric sliding gate. The gate's timing sequence starts as soon as the correct sequence of events causes it to open. At the prescribed time, the gate will start to close, unless it visibly knows the vehicle is still in the gate opening. With the gate's sensor mounted close to the ground, the high truck was invisible until the wheel tripped the sensor. A $450,000 Fire Engine with a scrapped front bumper.

Now we have a $450,000 truck with two static eliminators hung from the front bumper.

Bob,I remember when almost all cars had a piece of chain fastened to the chassis, hanging down and touching the ground...supposed to "eliminated Static" and that was supposed to counter motion sickness of the occupants. People prone to motionsickness did not get sick in a car when they saw that the car had a chain on.........All in the mind? [Seems to be far off the Fords convertion to 12v]

I can also remember something like this. I think people were taken to a "placebo" effect when they saw the ground strips...

But I also used such type of strips in two vw cars that used to accumulate static charge, and cause the passangers (because the driver - me - always waited for the passangers to leave the car first, of course) to receive a small but uncomfortable discharge when they touch the ground with the first foot in dry days.

Hum, a little bit off topic. But...

Actually, it was really funny.

The chain hanging from the cars that I owned when I was younger, were to allow me to be towed quicker when I broke it again.

You are correct. When I went back to the manual, it says that the 6 volt Fords were positive ground. The Op stated that he had polarized it already. Will the polarizing be lost if the battery is removed without the engine running?

Hello Bob

Will the polarizing be lost if the battery is removed without the engine running?

No, once it's polarised the field magnets retain residual magnetism, of the right polarity. When the engine is stopped the cut-out contacts are open and the generator is disconnected from the battery (the field is fed via the regulator contacts from the generator side of the cut-out. It needs the residual magnetism to start charging (positive feedback).

An alternator, on the other hand, doesn't (usually) retain enough magnetism in the rotating field to self-start. On modern alternators the charge warning lamp is earthed through the field and this current provides initial magnetism. This was discussed in a thread a few months back.

Cheers.......Codey

Mr Guy,

You must have forgotten polarizing. Earthing the Armature terminal will not polarize the fields of either the A or B type generators.

Sorry

jurie

Hello J

Don't like to speak for Mr. Guy, but perhaps he meant with the generator off the engine earth the F terminal and flash a wire from the batteryto the A terminal. This would have same effect as your piece of paper in preventing a short to earth when A is connected to the battery.

Codey

Carl -- this may be a long shot --- Is the current cutout switch in your regulator opening when the generator isn't putting out enough voltage (like when the engine is off or idling) and thereby allowing the battery to drain back to ground through the generator windings? Could be it's mechanically stuck closed, shorted or not even wired in. The test would be if you got any voltage reading at the generator terminals when the engine is shut off then you've got a problem. There should be none. Voltage at that point can and will drain the battery through the generator coils. On the other hand the cutout may be stuck in the open position or there may be an open or high resistance connection meaning that there is no way enough electricity can get through the regulator from the generator. So the car will just start and run off the battery.

This cutout was the answer to the problem before anyone had invented diodes. If you look at the 32-36 Ford 3 brush generators that little gadget mounted in a metal housing about the size of a plum on top is a cutout. That plus the adjustable third brush to set the voltage output was all they had on those cars. Up into the 40's Ford went over to the conventional voltage regulator with cutout, voltage control coil and current limiter coil in one box that lasted until alternators and diodes came on the scene.

Ed Weldon

Hello Ed

Don't think cut-out stuck closed is the problem. When that happens there is pretty much a dead short and wires can get very hot and burn out. If you accidentally press them together with engine stopped the reverse current holds them in, and unless you realise what's happening and pull them apart (likely getting a burnt thumb, but it's worth it!) or start the engine quick, you've got a burnout coming.

The regulator you describe sounds like the 3-bobbin type with separate current and voltage regulators. In UK we had plenty of 2-bobbin types, specially in early years, where current and voltage regulated by one coil. With that type the current drops off as voltage rises. With the 3-bobbin the current stays at maximum until voltage setting is reached, so should give faster charging. Alternator only has voltage regulation and charges at rated current until voltage setting reached (if it's turning fast enough) so behaves like 3-bobbin type regulator.

Cheers...........Codey

Codey,you have got it right mate!

J from SA

Thanks jurie!

On a 3-brush generator you movie the "3rd brush" closer to the brush to get higher voltage and current delivery. If battery is "gassing".. move brush further from A brush.

Just adding on!

But if Cutout points is stuck closed...the wiring will burn out due to battery-current shorting thru gen.-commutator to earth!

jurie sa

True, if all the contact points and connections are clean. I'm reminded of one little problem I was having with my old 41 Ford pickup. One day while I was in living in Texas the ignition on the hemi motor was acting up. After checking all the usual suspects I just happened to touch one of the connections on the coil. I burned my finger. Problem found; and easily corrected. High resistance allows some of the electrical energy to be released to form heat with the remainder continuing on to do the work where it is needed...... or not needed in the possible case of two failure points that we are dealing with here. Simultaneous failure of two related components in a complex electro-mechanical system like an automobile can be the most irksome to correct.

Ed Weldon

Hello Carl, Codey here, not logged in.

There have been plenty of responses to your OP. Did any of them help solve your problem? Be interesting to know.

Codey

13.5 volts is not high enough for a generator. As I recall normally a generator put out over 14volts under load(an alternator usually regulates about 13.8) . I'd suspect generator or regulator.

Carl. Carl. Where did you go?

I'll second that!

Codey

1940 Ford 6/12 Volt Conversion: You don't Mention the Distributor,Points & Condensor.Or is that included in your Terms: Mallory Ignition.

Each of these will likely work on either 6 or 12 volts. Except The Life span of the old 6 Volt Condensor, if supplied with 12 volts. If you have not already done so, I would check if the Distributor from the first years 12volt V/8 fits your '40' Flat head V8, you might try from a 1955 or 1956 models. Wish you well, Carl.

The 54 and up Ford Y block V8 distributor won't fit the flathead, either the pre-48 configuration with the distributor mounted on the front of the timing gear cover or the 49-53 style with the side mount distributor. 6 volt distributor mechanisms, points and condensers generally work fine on 12 volts. The one part that needs to be replaced is the coil.

For high reving and high compression modified flathead V-8's an aftermarket high performance distributor is usually necessary to replace the original Ford components. In the 50's and 60's when Mallory ignitions were readily available new for flatheads they were a very popular setup for street engines and were generally set up for 6 volts although they could use 12 volt coils. Mallory used the same high quality points, caps, rotors and fat brass cased condensers in both 12 volt and 6 volt applications throughout the 1950's. Nowadays there are electronic ignitions for flatheads in both the pre and post 48 versions available in the aftermarket although they take a bit of searching to find.

You do take a bit of a risk using 50-60 year old plastic ignition parts in engines today. Insulation deteriorates over time and some plastics, especially in aftermarket flathead ignitions other than Mallory, lose their strength no doubt due to the limited quality control over the plastic molding process that might characterize a small auto parts fabricator.

Ed Weldon

Use an alternator

25-30 years ago if you were running a street rod with a flathead and wanted to go 12 volts to make starting easier and allow the use of 12 volt accessories like modern radios the common setup was to use a Chrysler alternator. At the time there were a few repair shops that knew how to convert a stock 6 volt generator to 12 volts; but most of the street rodders weren't tuned into that if they hadn't read one of the articles on the subject in the magazines like Rod and Custom.

The somewhat ornate appearance of the aluminum castings on the Chrysler unit fits well with the usual finned heads and other chrome stuff on a modified flathead engine. The use of an alternator allowed a stock mounting location with some of the dual carb intake manifolds. It worked best with the 49-53 flathead setup which used narrow belts to drive the water pumps and generator. Fitting it to the earlier wide belt flathead setup could be done with the help of a machinist who could modify a pulley to fit on the Chrysler alternator.

It's important to note that the Chrysler alternators used a pulley with a substantial press fit so they could save the cost of a key and keyways. As a result getting that pulley off required a special puller. The use of a conventional gear puller of the kind found in the average mechanic's tool box usually ended in disheartening failure.

Ed Weldon

I have a 12V system on my '40 Deluxe and the gauges remained 6V. However, I have a problem with the fuel gauge not showing Fuel when the tank is full. Did you have this problem when you converted over to12v????

TKS

Mason

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