News (Stellpower)

Chrysler's alternators: a major gain over generators

Chrysler made Leece-Neville alternators optional starting with their 1950 taxi and police cars, but didn’t use them in regular cars. Alternators were better than generators in some ways—charging at idle, longer lifespan, and higher output—but they were more expensive, bigger, and pulsed at idle when hooked up to mechanical voltage regulators.

Glenn S. Farison, born in 1916, had numerous patents and inventions, covering small parts, tools, starters, and updated alternators. He died in 1988.

Chrysler had a fine electronics division, though, which developed an electromechanical voltage regulator. Then Glenn S. Farison invented a method for converting three-phase AC to DC through silicon diode rectifiers. Other diodes in his design made the circuit one-way—the battery wouldn’t turn the alternator into an electric motor!

Farison alternator rectifier patent

The invention made Chrysler the first automaker with standard alternators, starting with the 1960 Valiant. Their new alternator, the first to use diodes to convert power in a car, ran up to 60% of its peak capacity while the engine was idling, and eliminated the commutator, rotating armature, and current carrying arcs. It was smaller, lighter, and cheaper than the Leece-Neville units.

1960 alternator brochure

Chrysler made its alternators in Indianapolis; Essex Wire Corporation in Detroit, which supplied the wire and components, may have made some alternators. (Founded in 1930, Essex was taken over by Superior Telecom and became Superior Essex in 1998.)

The first alternators were just 30 amps, enough for some Piper airplanes but not for many cars; Chrysler increased the power but until they were able to reach 60 amps, they tapped Leece-Neville for heavier-duty alternators. Chrysler Canada, which did not make alternators standard until 1963, bought generators from Auto-Lite along with optional Leece-Neville alternators of 60 to 100 amps. (Eventually Auto-Lite’s parent company bought Leece-Neville.)

Chrysler 300G engine

All Chrysler alternators from 1960 through 1968, and most of the ones from 1969, connect one brush to a field terminal and the other grounded to the housing, to work with the electromechanical voltage regulator. This was constant even with the redesigned 1962 alternators. When the 60-amp alternator was standard on the 1969 Imperial and optional on other big cars, it used a special, single-year three-terminal electronic voltage regulator.

Dutch alternator brochure

Chrysler switched to an electronic voltage regulator in 1970 on all cars, enabling the new 1970-1971 “roundback” alternator; it used two terminals, one attached to each brush. In 1972 a new and more reliable “squareback” alternator eased assembly and service; instead of using six diodes, each of which had to be pressed in and soldered, it had two diode packs which attached without soldering or pressing. These (and the roundbacks) can be used in cars made before 1972, but only if the electromechanical voltage regular is replaced by a stock, 1970-up style “flatpack” voltage regulator. See Rick Ehrenberg’s full article. By 1975, Chrysler had a “100-amp” (actually 117 amps at maximum output) alternator.

1974 squareback Chrysler alternator

The Chrysler alternator pinnacle was in 1987, when two new alternators were launched, rated at 90 and 120 amps at peak output, or 40 and 50 amps at idle. They were, in size, between the 100-amp units and the original squarebacks. These were a completely new design, and the small numbers made are sought after by many seeking to increase their electrical power in their now-classic cars. For one thing, they can be repaired while on the car, by taking off the black plastic cover on the back and replacing the brush pack and diodes—for under $20. By this time, nearly every Chrysler car was front wheel drive and integrated the voltage regulator into the computer; the exception was the Fifth Avenue/Gran Fury/Diplomat, which (possibly along with trucks) kept the separate, external voltage regulator.

1988 Chrysler high power alternator

After 1989, Mopar bought all its alternators, at first mainly from Nippon Denso and Bosch—including 40/90 and 50/120 units. Daniel Stern wrote that these are “physically and electrically interchangeable — though there may be physical interference with other engine bay components in some cases.”

Alternators need the battery to be connected at all times because without the battery, the voltage fluctuates too much and can blow out the car’s electrical system.

Dating and identifying alternators

based on an Allpar story by Brian Kapral

The aluminum alternator case should not be cleaned with sandpaper or wire brushes, but by a soft brush and mineral spirits. Castings of rebuilt alternators are often hard to read due to the harsh cleaning process.

Lester suppied many castings for Chrysler alternator housings until 1965, stamping them just with their logo, the Forward Look rocket logo, and the casting number (2095191 or 2095192). They may still have date codes stamped as “date wheels” or pies stamped on the alternator housing, as Mopar’s own alternators did. In the middle was the year; around the circle, a dot showed the week within the month. Each section within the wheel was a month.

1960 Chrysler image

In 1972, Chrysler started stamping the part number and build date on a tag instead, though the housing still showed the build date. Round-back alternators have their date and part number cast in on a boss below the battery terminal. The date is a two-digit week and two-digit year, usually stamped underneath the seven-digit part number; more numbers may also be stamped there.

The alternator usually had date-coded diodes as well—four digits, the first three for the day (e.g. 225 for the 225th day of the year) and the final number for the year.

Alternators vs generators

based on an Allpar story by Wes Grueninger

A generator turns motion to electricity, using principles discovered by Michael Faraday. They were not practical for much of the 19th century; electrical current was mainly made by chemical batteries, which had to be regularly refreshed. Thomas Edison, realizing that current electrical theory was wrong, created the first efficient generators in the 1880s, before Nikolai Tesla got his first job.

Generators use a turning armature (a wire wound around a metal reel) with a set of brushes; the brushes carry all the current, which generates heat and limits their output. When the brushes pass over the commutator (a rotary electrical switch), sparks shortened their life; hard brushes lasted longer but wore out the commutator faster.

1974 squareback alternator (Plymouth)

Generators and alternators both need a way to cut power when they are not charging; otherwise the battery would turn them like an electric motor. Generators use a cutout relay for this, while Chrysler developed a diode set for the same purpose.

Alternators use field coils wound around a large bobbin, surrounded by iron shells. The rotating assembly (rotor) spins within a wire wound around a steel core (the stator). Alternators create alternating current, because the field alternates between the poles rapidly; the current is converted by the rectifier—the diode assembly—into direct current, which the car can use.

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