Model A Condenser and Cutout

This story only pertains to those Model A owners that have chosen to run on a generator.  First, if possible, choose a generator cutout made so that the cover is not welded to the base.  Your favorite Model A vendor should have such a unit.

Some of you may know how these “critters” work, but it may be a good idea to review a few details.  The circuit has a set of points very similar to the ones found in the distributor.  Over a long period of time they will carbon up and when this takes place the current that the generator is producing will not pass through them and the result is a burned out generator.

If you select a cutout that does not have the cover welded to the base, you can remove this part and clean the points, and thus, prevent the possibility of a damaged generator.  Cleaning will also eliminate the chance of points sticking should the spring be weak.

A tip for an emergency condenser is to buy a good condenser that has a “foot” on it and a “pig tail” about 3” long.  Loosen up one of the screws that hold the coil to the firewall, slip the “foot” of the condenser between the coil bracket and firewall and then tighten the screw down again making sure there is good contact between all units.  This gives a good ground connection.  Leave the “pig tail” hang free for emergency use.  Should your condenser located in the “A” distributor burn out, just loosen the coil terminal nut, attach the “pig tail” clip, tighten terminal nut again and be merrily on your way.  If you should wish to use this modification, the condenser will serve for years as it is located away from intense heat of the motor.  Heat is the worst enemy of the stock Model “A” Ford condenser.

This tech tip was provided by Bill Brex and was printed in the August 1993and November 1962 “A” Quail Call.

Discharging AMP Meter

During a restoration of a 1931 Panel Delivery, a situation arose that stumped Dick and his chapter members at the time, as they tried in vain to solve the problem of a discharging AMP meter.  After installing a new generator, a cutout, polarizing it and recharging his battery, none of which helped.  What was the solution…reversing his wires to the AMP meter.

This tech tip was provided by Dick & Sherry Huff and was printed in the July 1993 “A” Quail Call.

Ignition Coil Connections

The ignition coil does not change the direction of current flow hence it does not change polarity.  However, there are more coils in the secondary winding inside of the coil, thus there is more resistance to incoming current flow at the secondary winding terminal, so the coil’s high voltage output to the spark plugs will be less if the battery is inadvertently connected to the secondary winding terminal.  By the way, the higher resistance wastes primary current in the form of heat and the coil will run hotter if the battery (current-in) is connected to the secondary terminal instead of the primary terminal.  Heat reduces coil life!


So now that we know the primary terminal on the ignition coil is where we want to connect the battery wire, two questions arise to get the connection right in the Model A: (1) Which is the primary terminal on the coil? (2) Which is the correct wire from the battery that connects to the primary terminal?

    (1) Using an ohmmeter with one lead in the high voltage output socket, measure the DC resistance at each wire terminal.  Connect the battery wire to the terminal with the least resistance to get the highest secondary voltage output to the spark plugs.

    (2) Assuming that the Model A has a 6-volt system wired in accordance with the factory diagram, the BLACK wire from the driver’s side of the terminal box is the correct wire. If your Model A has non-factory wiring, then find the wire coming from the CHARGE side of the ammeter and trace it down to the terminal box stud.  Connect this stud to the primary terminal of the coil.


Do not rely on the markings that may be cast into the coil top at the terminals.  Before 1955, coils were marked  (-) or BAT at the primary winding terminal, and (+) at the secondary winding terminal because the ignitions of the time were 6-volt (+) ground.  By 1956, ignitions went to 12-volts (-) ground, so the primary terminal was marked (+) or BAT.  So you can see the coil markings may cause you to make the wrong connections for a pre-1956 Ford.


If you find the above confusing, here is a much simpler solution.  Buy from your local Model A parts supplier, a gizmo known as a “Ignition Spark & Coil Tester.”  It costs in the ballpark of $25, and it has lights to indicate if the wiring is right or wrong.  This gizmo will earn its price back in gasoline mileage and performance.


Most all coils, 6 and 12-volt alike, for breaker point ignitions are (the same) designed for 6 to 8-volt operation.  Note the resistance wire in the figure.  In a 12-volt ignition system, the ignition switch has 2 run positions.  The START position allows 12 volts into the primary coil to get a hot shot high-voltage engine start.  When you release the key to the RUN position, the resistance wire is cut into the primary circuit to drop the coil voltage to 6 to 8 volts.  The heat from a constant 12-volt input will shorten the life of a breaker point ignition coil.


When converting from 6 to 12-volt operation, you can run a reproduction “Ford” script 6-volt coil with an external resistor so the coil operates at 6 to 8 volts.  You can also run a 12-volt coil with an external resistor.  However, some 12-volt coils have an internal resistor and you need to know this to avoid having two resistors on the primary side of the coil.


Running an antique ignition coil is fool hardy because eventually coils breakdown and cease to function without warning.  Do not run an original antique coil in a 12-volt conversion because these old coils will not take the stress of 8 to 12 volts.  Also make sure that the brass terminal ends are soldered to the conductor of the high-voltage wire between the coil and the distributor.  Keep the primary wire connections bright & tight and the plastic parts of the coil and distributor clean.

Anatomy Of A Good Solderless Terminal Connection

One of the people who looked this article over asked why I didn’t title it Anatomy of an Aircraft Quality Terminal.”  I would probably have done that twenty years ago; now I’ll suggest that the term “aircraft quality” has no quantifiable meaning.  But that’s a topic for another article.  For now, take a few minutes to understand how a really GOOD terminal is made, how it works and what techniques are required to utilize its capabilities.

The first figure illustrates major components of a good terminal.  Item 1 is the electrically conductive portion of a solderless terminal.  It’s made from copper and generally plated with tin to forestall corrosion.  Terminals are fabricated in a variety of sizes for both stud size (hole) and wire size (barrel i.d.).  In some products, the bare, uninsulated terminal is sufficient for bringing a wire up to a stud.  Bare terminals can be used where there are no vibration concerns.  They’re commonly seen in a variety of non-vehicular application.

When any amount of vibration is anticipated, it’s important to support the wire close to but separate from the wire grip on the conductors.  Flexing of the conducting strands where they leave the back of the terminal barrel must be controlled.  Like aluminum, copper is one of those non-ferrous metals that readily stress cracks.  When any flexing occurs in the stranding between terminal’s wire-grip and end of the wire’s insulation, hardening of the wire will occur, precipitating cracked strands and a failed connection.

The standard technique for adding support is to slip a malleable plastic sleeve over the terminal barrel and leave it long enough to permit a second, insulation supporting crimp.  The plastic sleeve is generally made from nylon but other plastics are suitable.  The vast majority of off-the-shelf solderless terminals offered by electrical and automotive parts stores are two-piece devices consisting of terminal (1) and insulation support sleeve (2).  These terminals are not recommended for use in airplanes.  The plastic wire-grip sleeve has a memory.  Temperature cycles encourage a pure plastic support sleeve to recover its original round shape!  You lose wire support leading to probable failure of the connection.

About 50 years ago, a third component was added to solderless terminals to prevent this problem.  Item 3 is a copper sleeve slightly shorter than the plastic sleeve; a metal liner inside the plastic.  When the insulation grip crimp is made, the copper liner becomes a permanently formed wire support, effectively overriding any memory characteristics of the plastic insulator.  A more obscure feature of a good terminal is a “funnel” shaped entry (item 4) at the back of the wire grip barrel.  Not every terminal with a metal lined insulation grip will also have funnel shaped wire guides but they are really helpful.  Square entry to the wire grip barrel will more likely snag single strands of wire causing them to fold back under the insulation where they are difficult to detect.

The best terminals are readily identified by inspection:  Just look to see if there’s a thin copper liner inside the plastic.  These terminals are manufactured by many manufacturers including AMP, Inc. as their “Pre-insulated Diamond Grip” (PIDG) brand and Waldom-Molex in their “Avi-Crimp” brand.

There’s a range of styles in crimping tools.  MOST will properly install a terminal.  The trick in terminal application is to achieve the proper HEIGHT of finished crimp.

The figure above illustrates the relationship between crimp height and two important terminal parameters:  electrical resistance and mechanical (tensile) strength.  As crimp height decreases, electrical resistance goes down while tensile strength goes up.  At some point, both parameters level off showing that further crimping doesn’t make the joint any better.  Continued reduction in height will eventually upset the strands too much.  Strength goes down and electrical resistance starts to go up.

The best tools have ratchet handles.  The mechanism prevents under-crimping by forcing the user to operate the tool through its total stroke.  When the tool is fully closed, sculptured dies enclosing the terminal barrel work against hard stops thus insuring uniform crimp height.  Ratchet handled tools will also do a complete terminal installation with a single stroke.

The Low Cost Alternative

Just about everyone has a stamped, sheet metal, rivet jointed crimping tool in their toolbox.  These tools are commonly supplied with a kit of terminals and splices by automotive parts stores in a compartmented container.  These tools are capable of producing satisfactory crimps but they require some practice.  The terminals that are sold with them need to be saved for use on your washing machine or stereo speaker system.

First, strip outer insulation from the wire so that when fully seated in the terminal, the ends of wire stranding should just protrude from the stud side of the crimp barrel.  Center the appropriate die on the tool over the wire grip section, approximately 1/3 of the way from stud end to entry end of sleeve.  Apply firm grip pressure but it won’t take a great effort.  When you think you’ve done it about right, tug on the wire to the tune of 5-10 pounds for 22AWG wire and up to 20 pounds for 10-12AWG wire.  What??  You don’t know what an 8 pound pull feels like?

Here’s an accurate, poor-man’s pull test for terminal application:  (1) Drive a finish nail into the front of your workbench.  (2) Hang the terminal lug on the nail and tie a plastic gallon milk jug of water onto a 22AWG wire (red terminals).  For 18AWG (blue) use two jugs.  For 12AWG (yellow) use three jugs.  The task is to “calibrate” your grip.  The range of pressures required to produce an adequate crimp are quite large and for the most part, you have to really work at over-crimping with low-cost hand tools.

The second crimp is 2/3 of the way along the barrel closed just enough to grip the wire’s insulation…generally MUCH less pressure than the amount required to grip the wire.  There’s some old’ mechanic’s tales wandering around out there suggesting that wire grip and insulation grips should be put on 90 degrees displaced from each other.  This is not a helpful technique and, in my not so humble opinion, makes for a crummy looking terminal.

The plastic insulator of a finished crimp should have a smoothly sculptured appearance; no sharp indentations or cracked insulation.  Some low cost tools punch an indentation into the side of the terminal barrel.  These tools are for uninsulated terminals on solid wire.  The shapes of proper crimping dies range from oval to rounded-rectangular but in no case is the resulting crimp anything but smoothly molded around the terminal barrel and wire.

Dispelling a Myth

Some folks recommend a combination of soldering in addition to crimped joints for reliability.  Keep in mind that the Boeings, Beeches, Pipers and even the lowly Cessna’s haven’t soldered terminals on a wire in over 30 years.  People like AMP and Molex have carved an honorable place for themselves in the aviation marketplace selling termination systems that do not require solder to achieve the highest levels of reliability.  Please forget the solder.

This tech tip was provided by Bob Nuckolls and originally printed on the Aero Electric Connection website and with permission was printed in the August 2003 “A” Quail Call.

Converting Your Model A To A 12 Volt System

The rule that makes 12-volts work so well is the one that says if you double the voltage, the amperage required to power that same accessory is reduced by half.  For example, the original 6-volt motor requiring ten amps of electrical current would only need five amps of electrical current to run at the same speed.  So with this, the total load for the Model A with the lights on running at night and trying to blow the horn would only be half as much with a 12-volt system as with a 6-volt system.

Six-volt electrical systems use heavier gauge wiring to deliver the higher amperage draw.  Therefore the wiring does not have to be changed when converting to 12-volts.  Also the windings in the starter and horn are also heavier due to the amps used in a six-volt system.

If you are still using a six-volt generator it can be converted to 12-volts.  You will need to have the field coils (magnets) replaced.  These are the magnets that are attached to the inside of the generator case.  This is a job that can be handled by any qualified alternator/starter repair shop.  You will then need a 12-volt regulator.  Just ask for a 1956 or newer 12-volt regulator to match your application.

Alternators were first introduced in the early 1960’s.  By the 1970’s alternators were being built with solid-state internal regulators.  This improved the reliability of vehicle charging systems.  The biggest difference between an alternator and a generator is that an alternator is able to produce a strong electrical output at idle and low rpms.  This makes the headlights bright all the time, and provides a way to keep the battery fully charged at all times. 

An alternator generates electricity just the opposite way a generator does.  Inside an alternator, the armature remains stationary while the field coils rotate.  That makes the alternator able to spin up to 10,000 rpms before suffering any internal damage.  Therefore a smaller pulley can be used on an alternator to keep the rpms up while idling.

The best alternator to buy is a General Motors 10SI series alternator.  You will want to have the alternator made into a single wire alternator.   These alternators are also available through your Model A vendor.

You will have to change all your light bulbs to a 12-volt lamp.   This will make the lamps you use a standard lamp available at your local automotive store.  This convenience will help eliminate the amount of parts that you will need to carry.

Your Model A was built with a positive ground system.  This means that the negative (-) terminal of your battery is connected to the starter terminal and the positive (+) side of the battery is connected to ground.  In order to use the above modern alternator on 12-volts, you will need to reverse the polarity.  When this is done, you will also need to reverse the wires on the amp gauge in the dash and the coil.

The ignition coil will either need a resistive ballast added to the incoming power or my recommendation is to buy a coil with an internal resistor.  Internal resisted ignition coils are much more reliable and will eliminate a common trouble spot, the external ballast resistor.  One coil that you can get is a NAPA Echlin PT# IC64.  Remember that this coil needs no external resistor.

Last but not least, you will need a 12-volt battery.  Make sure to measure your battery box, so you can get the right dimensions for your new purchase.  I would recommend that you find one with the cold cranking amps close to the six-volt battery.  Happy driving.

This tech tip was published in the March/April 2002 “A” Quail Call.

Condensers and Coils

Condensers:  You can tell when a condenser has gone bad if your normally smooth running engine suddenly backfires and won’t rev up.  One way of checking this out is to remove the distributor cap, body and rotor.  Make sure the points are closed.  Turn on the ignition switch and place the high tension wire (from center of coil) about 1/2” from any convenient ground on the engine.  Push points open with a screwdriver then close the points.  The spark should jump the gap with a sharp crack and a straight line.  The spark should have a blue tinge.  If the condenser is bad, the spark will still jump the gap, but will be thin and stringy and white in color.  Whenever in doubt throw the condenser away, especially if it is a new reproduction condenser.  These cannot always be depended on.  If you happen to have  used condensers and want to have their condition checked, take them to your local TV or radio repairman who has the necessary equipment to check them.

Coils:  Begin by turning off the ignition key.  Remove the tension wire from the center point on the coil.  Remove the black wire from the terminal (- side) on the coil and the red wire on the (+ side) of the terminal on the coil.  Using an ohmmeter (lowest scale), measure the resistance from the (+) coil terminal.  This should measure 1.6 ohms to 1.8 ohms.  Now set the ohmmeter to 10K scale.  Measure the resistance from each coil terminal (+) and (-), to the center contact.  This should measure 6.7 ohms to 10K ohms.  Measure the resistance from each coil terminal (+) and (-), to the outer metal case of the coil.  Now you should measure as an open circuit.  If the first two steps show a short or open reading, it indicates a defective coil.  If the 10K step shows any reading except open (infinity), the coil is defective and should be replaced.

This tech tip was originally printed in the September 2000 “A” Quail Call.