I've owned my 36 Packard Senior 8 1401 Rumble Seat Coupe for over fifteen years, having restored/preserved it from bumper to bumper.  This is one of my cars that is rarely driven, and spends way too much time in the garage.  I keep a maintenance log on all of the cars, but even so, sometimes one or two just don't get started.  As a safeguard, I keep non-ethanol gas with preservative in them and use battery maintainers.  This way, the gas is usually good for 6-7 months.  Somehow, the '36 didn't get started for eight months.  When I went out to start it, I checked the glass fuel pump and carburetor filter bowls, and the gas was orangenot a good sign!  We drained the old gas and replaced it with five gallons in a 25 gallon tank, so that the gauge would read 1/5 tank, and that way I would know if the float was working in the gas tank.  I replaced the fuel filter, checked for moisture in the oil and for spark at the plugs, and started the car.  It ran terribly!  It wouldn't idle, throttle, had no power, the gas gauge was stuck on tank, and no charge was coming through the amp gauge.  Other than that, as they say, everything was perfect.

        I removed the air cleaner while Jason held up the throttle, and I could see gas dripping down the throat as it ran (faulty accelerator pump).  I sent the carburetor to Daytona Carburetor* for a rebuild and the stuck and corroded sending unit to Bobs Speedometer* for rebuilding, which still left the generator's no charge problem.  I had rebuilt the generator and dash amp gauge, put in new wiring and replaced the voltage regulator just before the car sat for eight months.   Packard Senior cars in 1936 used a silent chain gear-driven generator with a brass adapter.  The nose of the adapter allows the gear's bearing to ride on it and the armature's teeth fit into the gear on the timing chain.  In removal or assembly of the generator, if the gear is knocked out of the timing chain, the radiator/grill shell, radiator and timing gear cover have to come off.  We did this once before, during the engine rebuild, and is it a big job!  With the parts out for rebuild, I felt it was a good time to research the charging system, to know how it works, and have a plan to possibly fix it on the car or to remove it with the least chance of destruction.  




        1.  You first determine what kind of generator you have.  Before alternators, most early cars used (1) 3rd-brush Generators through the mid-'30's, (2) Shunt-type (2-brush) through the '50's until alternators became industry standard.  

        2.  How is the generator groundedinternally or externally?  (This will determine how it is polarized.)

        3.  What is the generator's output (amps)?

        4.  What is the voltage regulator output? (volts)

        5.  How to polarize the generator.    

        Our '36 has a 3rd-brush generator, and is externally grounded.


        What is a 3rd-brush generator?  This generator uses the third brush as an internal means of controlling the maximum output of the generator.  The field circuit is connected to the third brush, so that the current fed to the field windings is taken off the commutator by the third brush.  The two main brushes are located on the commutator at the two places between which there is maximum voltage.  The third brush is placed between the two and consequently picks up less than the maximum available voltage.  By moving the third brush toward the adjacent main brush, the voltage across the field and the current through the field windings can be increased.   Additional field current increases the strength of the magnetic field, causing a higher generator output.  By moving the third brush away from the adjacent main brush, the voltage across the field windings is reduced, less current will flow in the fields, and the generator output will be decreased

        The 3rd-brush generator was originally used in the automotive industry because of its simplicity and because it was easy to regulate generator output by changing the position of the third brush.  Another benefit was that the 3rd-brush generator tended to regulate itself and, within limits, would not produce an excessive amount of current.  In a two-brush shunt generator, without some form of regulation the voltage could become excessive at high speeds.  High voltage would result in excessive current flowing through the field winding, developing an excessively strong magnetic field, which would further increase generator voltage and output.  This increased voltage and current would ultimately cause the generator to overload and become overheated.  The 3rd-brush generator is not subject to excessive overloading since it is generally self-regulating and normally can not produce too much output if the third brush is adjusted properly.


        Factory or Motors manuals will indicate the type generator for your car, as well as the output.  Manuals will also provide a diagram, but sometimes don't specify how it is grounded.   To determine the ground, look at the diagram to see how the ends of the field coils are connected.

        EXTERNALLY GROUNDED (Type A Circuit, as used on Packard, GM and most other carssee Motors manual for your type) has the field connected to the insulated main brush (on ours its the third brush) inside the generator, with the opposite end of the ground, or return circuit outside the generator usually grounded in the coils of the regulator.

        INTERNALLY GROUNDED (Type B Circuit, on Ford products and otherssee Motors manual for your type) generators have field circuit connected to ground inside the generator with the opposite end of the field circuit connected to the insulated side of the circuit outside the generator.

        Another way of determining external or internal ground without a diagram, is to use an ohm meter to check armature and field for continuity.  To check for External Ground remove one brush (doesn't matter which one).  This will not show a break in continuity between the armature and field.  For Internal Ground remove one brush.  This will show a break in continuity between the armature and field.  

        GENERATOR OUTPUT:  Our Packard manual showed our generator output as 30-33 amps cold and 27-30 amps hot, regulated output 6 - 7 volts.

        POLARIZING:  For an externally grounded  generator, with key off, polarize using a jumper wire to momentarily touch the battery and armature (gen.) poles of the voltage regulator.  This will produce a flash, not a severe spark.

        Internally grounded generators are polarized (key off) by connecting all leads but the one to the generator field or "F" terminal.  With a jumper wire, connect momentarily from the insulated battery terminal to the "F" terminal.  There will be a flash and the generator will be polarized.  Then, re-connect the "F" terminal lead.  It is imperative to know how your generator is grounded, because incorrectly polarizing can burn out the armature and the voltage regulator.

        With this information we were ready when we got our parts back.  The rebuilt carburetor and sending units worked great.  We pulled the car outside to reduce gas fumes, and polarized the generator.  (When a car sits, especially if battery disconnects are used, the generator (voltage regulator) can lose its magnetism, resulting in the need to re-polarize, even if nothing was disconnected from the charging system.

        Before polarizing, Jason cleaned the voltage regulator points with a riffler file (cupped file for voltage regulator points), then polarized "batt" to "gen" and got a flash.  To test the generator voltage output, we used a volt meter, putting one lead on ground and one on the battery pole of the voltage regulator, and with the car running, the reading on the volt meter was 6.1 volts.  Revving the engine showed no change.  The reading should have been 7.4 volts max.  The problem was now clearly with the generator.  Adding up the clues led us to oxidation on the armature and brushes.  Jason removed the generator's band covering the brushes and sprayed electrical contact cleaner (non-flammable type) on the turning armature as the car ran.  In about a minute, the dash amp gauge needle jumped to the positive.  The generator was charging!

        Now, everything is working and we know a lot more about vintage charging systems.  With less and less information out there about generators and polarizing, I hope this helps.  The one lesson that I won't have to learn again is to start and drive the cars on a designated schedule--no exceptions!  

         Enjoy your cars, and keep em driving!

        Of course, all safety precautions must be implemented--disconnecting the battery when necessary, use of safety goggles, rubber gloves, etc.