Alternator Date Code Markings

Now on to the markings of the Chrysler alternator. As you know Chrysler went to great pains to mark and identify almost every part that went into the creation of all their cars. The alternator was no exception. Both the front and rear frame had a "pie" casting date cast into the frame when it was made. This was divided into twelve sections each representing a month of the year with the year cast into the center of the pie. Each section of the pie had raised dots identifying the week of the month that the frame was cast. Three dots in the third section of a pie with a "69" in the center would mean the frame was cast in the third week of March 1969. The front and rear frames on any particular alternator may or may not have identical casting dates. They could vary by several weeks or even months. At the time the alternator was then assembled, the date code was stamped on the pad above the battery terminal just below the part number which was also stamped into the rear frame. This was a three or four digit code with a space between the first or second digit and the third digit. The first and/or second number was the week and the last two digits was the year that the alternator was assembled. A date of "1 68" would mean the alternator was assembled the first week of January in 1968. A date of "42 68" would be the second week of October 1968 and would be used on a 1969 model year car, since the new model years began in the fall of the previous year.

On a correctly coded alternator the assembly date must be later than the casting dates of both the front and rear frames and earlier than the build date of you car. The bottom of the diodes also had identifying numbers printed on them. Most of the diodes were manufactured by Motorola for Chrysler. Some had the Motorola symbol, which was the letter "M" inside of a circle, printed in the center of the diode. Around the outer edge of the diode was the Chrysler part number and the manufactured date of the diode. The date code on the diode was also a four digit date of which the first two numbers designated the week of the year and the last two the year, similar to the assembly date of the alternator except that there was no space between the numbers. These dates must also be earlier than the assembly date stamped on the alternator, but not always earlier than the casting dates on the frames. Chrysler also attached a red warning tag to one of the field terminal spade connectors on the back of the alternator. It read "WARNING DISCONNECT REGULATOR BEFORE TROUBLESHOOTING". This was put on the alternator because when repairing the charging system even an intermittent grounding of the field wire would burn out the voltage regulator.