Alternators and Generators
This page covers a brief history of Chrysler and the alternator; alternators vs generators; and troubleshooting alternator problems.
Experimentation for automotive alternators rapidly expanded in 1949, based on military use during World War II. They had numerous advantages over the generators which came in every non-fleet car until 1959:
- Alternators charge while the engine is idling, reducing battery use and allowing for more use of electric accessories (seats, windows, radios, etc.)
- Alternators can have a much longer lifespan because the brushes don’t handle their full power
- Alternators can create far more power than generators, in automotive use
On the down-side, early alternators used mechanical voltage regulators, resulting in pulsing at idle. That was eventually fixed by using electronic regulators.
Dodge started selling Leece-Neville alternators as options in their taxi and police cars as far back as 1950, and later had them as an option in Power Wagon. By 1957 (possibly earlier), Ford had optional alternators in police cars and ambulances.
Chrysler opened their own electrical parts plant (Electrical Equipment Division of the Automotive Manufacturing Group) in 1958, in Indianapolis, Indiana, near their Kokomo aluminum die-casting operation. The Automotive Manufacturing Group also managed all the assembly, forge, foundry, engine, stamping, axle, transmission and parts plants in the U.S.; it had been formed in 1957, although the assembly plants outside of Detroit formed the Regional Car Assembly Group before then.
Glenn S. Farison was listed as the inventor on Chrysler’s patent number 3,184,625 on May 2, 1960; it detailed a rectifier which used diodes to convert alternating current to direct current (AC to DC), and to prevent the battery from turning the alternator into a motor, as well as construction methods of some components.
The invention helped Chrysler to become the first automaker to include an alternator as standard equipment in their cars, starting in 1960. As the patent application claimed, “The alternators heretofore supplied for commercial and special purpose passenger carrying motor vehicles have been expensive, large size, inefficient, noisy units...” Farison’s, by converting three-phase AC to DC through silicon diode rectifiers, operated at up to 60% of its capacity while at “the slowest engine idling speeds.” It eliminated the commutator, rotating armature, and current carrying arcs.
Chrysler was the first to use diodes to convert power, and also was the first to use electronic voltage regulators, both byproducts of their Defense Department research. Using electronic rectifiers (AC-DC converters) and voltage regulators eliminated periodic maintenance.
The use of the alternator on the Valiant went with its brand new image - new body, new unibody construction, new engine, new-ish transmission, and new brakes.
Chrysler made their alternators at Indianapolis, Indiana. Chrysler used Essex Wire Corporation (Concord Avenue, Detroit) for electrical wire and components, and possibly for assembly of some alternators. Founded in 1930, Essex moved to Fort Wayne, Indiana in 1964, and in 1998 they were taken over by Superior Telecom (née Superior Cable) and became Superior Essex.
Chrysler Canada did not offer the alternator as standard equipment until 1963, even on the Valiant; they purchased generators from Auto-Lite’s Sarnia (Ontario) factory, while selling optional Leece-Neville alternators of 60 to 100 amps. (The Electric Auto-Lite Company of Toledo, Ohio had been Chrysler’s main ignition and electrical supplier since 1935.)
Mopar Action’s Rick Ehrenberg wrote:
Early units were rated starting at 30 amperes, okay for a dead-stock 1960 Valiant, but add in a few kicker stereos or rear window defroster, and the stocker is quickly overwhelmed. Mopar responded to the need for juice with ever-increasing current-output ratings, and two entirely new alternators: a massive 100 amp (nominal, 117 max) unit in 1975, and a more compact (than the 100amp) unit in 90 and 120 amp versions, put into production in 1987 and discontinued by 1989! After that date, all alternators in Mopars were “purchased.”
Begin with the 1972-up “squareback” unit; these are much more reliable than earlier versions due to the bolt-in diode block which eliminated all soldered connections. If your car is pre-1970, use a stock, 1970-up style “flatpack” voltage regulator. (Swapping this into earlier cars is about a 20-minute job.) See Rick Ehrenberg’s full article
Daniel Stern added:
The 1960-61 and 1962-up alternators had many differences.
All Chrysler alternators from 1960 through 1968, and most of the ones from 1969, have one single field terminal protruding from one of the alternator brushes; the other brush is directly grounded to the alternator housing. This setup was to aid usage with the electromechanical voltage regulator.
For 1970, the electronic voltage regulator was standard equipment on all passenger cars, and 1970 and 1971 “roundback” alternators, like the 1972-up units, have two
field terminals, one protruding from each brush, for the two-terminal electronic voltage regulator. Sixty-amp alternators in 1969, which were standard equipment on the Imperial and available on other big cars, used a special one-year-only 3-terminal electronic voltage regulator.
The 1972 and later “square-back” redesign was for ease of assembly and service. Instead of six individual, pressed-in diodes that each required a solder connection, they had one positive and one negative unitized diode trio, no press or soldering iron
needed for removal or installation.
The Chrysler 40/90 amp and 50/120 amp (idle and maximum) alternators were smaller than the giant Chrysler 100 amp units, but at least as large as the original roundback/squareback alternators. They were a completely new design. The Bosch and Nippondenso 40/90 and 50/120 units Chrysler also purchased were both smaller. All six, however, are physically and electrically interchangeable — though there may be physical interference with other engine bay components in some cases.
Hemi Andersen wrote about the compact 90 and 120 amp 1987-89 alternators: “Of all optional alternators, this is by far the finest design. I use only these alternators on my cars wherever possible. They are far better than the Nippon and Bosch alternators, in that they can be repaired on the car: by taking off the black plastic cover on the back, you can replace the brush pack and the diodes. I have only replaced the brushes on one of my alternators in all these years. Anyone who pays for a rebuilt alternator of this type could have fixed it for around $12 to $15 by replacing the brushes.”
Finding alternator dates and types
Alternator housings can be cleaned without damage by using a soft brush and mineral spirits, rather than sandpaper or wire brushes.
Most Chrysler-built alternators have date codes on them — except some from 1960-65, whose castings were supplied by Lester; this company only included their logo and the casting number (2095191 or 2095192), with a Forward Look logo on the back casting.
The casting number on pre-1972 alternators is a date wheel; the two-digit number in the middle shows the year, and a dot is placed around the circle to show the week within the month (each “pie” section is a month). Starting in 1972, the company still showed casting dates, but the part number and build date were stamped on a tag attached by one of the through bolts.
Round-back alternators all have a build date and part number cast in on a boss just below the “batt” terminal; the part number is a seven-digit part number with a pair of numbers, usually stamped underneath it, showing the two-digit week and the two-digit year. There may be additional numbers whose purpose remains unknown.
The alternator was usually made weeks to months before the car, and usually had date-coded diodes (four digits, the first three for the day, e.g. 225 for the 225th day of the year, the last one for the year), made before assembly of the alternator though not necessarily before the casting. The castings of rebuilt alternators have usually been somewhat damaged by the cleaning process; rebuilt alternators often used machined pulleys, for universal use, rather than the original stamped pulleys. Finally, the rear bearing will usually be flat if it was rebuilt; the original bearings had some raised ridges.
Chrysler used zinc-plated screws until mid-1969, then used both zinc-plated and black phosphate into 1970 before the black phosphate screws dominated; the black screws are reportedly harder to remove and easier to break.
Some information courtesy of alternator rebuilders Plum Crazy Garage.
Alternators vs generators
Generators use an armature (wire wound around and around) surrounded by a set of unmoving field coils, like a DC motor. The field coils are powered, and the regulator controls current to the fields to control the output of the generator. As the armature turns, electrical current is induced in its windings.
Generators had very clean electrical output, since they produced pure DC. However, all the current had to travel through the brushes and brush leads; this produced a lot of heat, and when the brushes would pass over the bars in the commutator, small electrical arcs would be produced, which shortened the life of the brush. To counter this, the brushes were made very hard, which wore out the commutator faster. Because all current traveled through the brushes, most generators had a maximum output of 50 amps.
Generators needed a cut-out relay to cut power to the generator when not charging, so it would not pick up power from the battery and turn into a motor, burning out when not being spun by the engine.
In alternators, the field coils are wound around a large bobbin and surrounded by two interlocking iron shells. The coil is attached to two copper slip rings; the regulator powers them through metal brushes to control charging. The whole rotating assembly is known as a rotor.
In the alternator, there is wire wound around a steel core, called the stator. The rotor spins inside of the stator. As the rotor spins, the alternating between north and south poles induces a current in the stator. The current is alternating current - hence the name “alternator.”
The current from the stator passes through diodes - three or four positive diodes and three or four negative diodes, which “rectify” (which is why the diode assembly is called a “rectifier”) the alternating current into direct current.
Current alternators can produce over 160 amps; the brushes only carry current to power the rotor (about 7 amps, maximum), so they last far longer than generator brushes do. There are some disadvantages, though. The Lundell alternator requires two watts of power to spin for every one watt that it produces, making it relatively inefficient.
There are several new alternator designs out there - General Motors has gone to water-cooled alternators to keep the diodes cool on some cars. Several companies now use combination a starter/alternator built into the flywheel to allow for stop/start and hybrid systems.
Troubleshooting (from “Wizard”)
- The alternator generates AC voltages, then diodes block one way and let power though in other way, that gives you some rippling DC but battery smooths this out. Without the battery, or if either positive or negative hook ups on battery itself go bad, voltage rises and can hit 40V. Pop pop pop! go the electronics and bulbs.
- A short in the alternator diode array creates a whine in your radio speaker.
- Automakers have been talking about moving up to 36 volts (from the current 12 / 14.5) for some years, because there are fewer power losses as voltage increases.