Identifying Chrysler Alternators (1960-1976)

My 1982 Dodge Aries had the square-back alternator in a transverse 4 cyl engine (2.5L, based on slant-six block w/ 2 cyl lobbed off). The alternator was bad when I bought it and failed again several times. Each time, the 3 positive diodes disappeared (post 1, 3rd photo, top 3 diodes). Those are isolated from ground, and conduct heat to the floating rail, plus the air. In the round-back, those diodes also float but are pressed into a thicker aluminum holder. Regardless, the square-back seems to work fine in earlier longitudinal engines, so my guess was it didn't get enough airflow when sideways. Instead of always having to unbolt the AC compressor to work the alternator out, I got good at splitting it apart underneath the compressor and replacing just that diode assembly. By cutting "cooling fins" in the rail, I got them to last 2 years instead of the normal 1 year. A guy at an auto electric shop who sold the innards parts said that was a common failure. The 3 negative diodes (at bottom) are bolted to the case so get adequate cooling.

The only cabin monitor was a battery idiot light, that when it came on you were almost done and might barely start and make it 20 miles, since they decided the dash ammeter was too confusing and added expense. Today, you can get a little cigarette-lighter voltmeter (some w/ USB charger) if your ammeter is bypassed. You should read 14.3 V while driving if the alternator and Vreg are working.