When my parents got their new 1972 Chrysler, I noticed the a/c compressor running at times that the one on our '66 Chrysler did not, even with the "OFF" button pushed. What the local service manager told me was that they designed them to do that. When "OFF" was pushed, the evaporator fan didn't really stop, but ran at a very low speed with output toward the windshield for air circulation and demisting. The compressor also ran to help dehumidify things too. He mentioned also that the police vehicles came with a cut-out switch for the compressor during pursuits or times they didn't want the compressor to run. Although it sounded unusual, I found his comments to be correct.
What I also discovered was a switch on the "TEMP" lever, about half way between "Cold" and "Hot" in the lever's travel. It was a switch to turn off the compressor at the higher heat settings. With the normal manual a/c system, I could reposition the wire on the hot water valve under the hood to be closed when the lever was just past the switch's "off compressor" point. It looked a little funny, but it worked.
From what I've seen of the Chrysler AutoTemp system, it makes the similar GM system look crude. The GM a/c systems also had an ambient temp switch in the compressor circuit that kept the compressor inactive if the temp is below a certain temp (somewhere near 32 degrees F.)
When fuel economy became a concern, many of the automatic a/c controls also had an "Econ" position or a switch to turn the compressor off manually. The Chrysler automatic a/c controls on the first gen LH cars is highly automated in operation, but will also allow manual control if desired--if it's on automatic mode and you make a particular manual adjustment (as in changing the air flow pattern), it will kick out of automatic and revert to full manual operation. There's also a "snowflake" button that controls the a/c compressor's operation too.
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