I wired a temporary harness from the alternator output to the cab of the HHR. Then I connected a Fluke 87 and set it to MIN-MAX and went for a drive to see how much it varied. After 5 miles and the light coming on twice, briefly, the minimum voltage was 12.8 and the maximum was 14.7. The average was 13.6, all good numbers.
Then I drove to O'Reilly's and had the system checked like one person suggested. The employee found that the battery was on it's last leg, even though it held a charge and passed the load test- barely. The alternator was OK. Costco was out of the battery I needed, but will have some in stock on Wednesday.
I ordered a Foxwell Battery Analyzer on Amazon so I can do this test in the future myself. I have 3 other cars and an RV, so there's a lot of batteries to potentially go bad!

 

See #19

 

I was reading voltage directly off of the output terminal on the alternator to see if it was over/under charging. I ran 2 wires into the passenger's seat and could read and record what the output was while driving under various conditions. A flawless way to do it, you would have been impressed!
The diodes were tested with the correct tool later.

 

As I suggested in post #2 have the battery load tested. Seems to me the load test revealed a dead battery.
You stated in post #3 the battery load tested ok, did you mean a VOM test showed 12.4 or more volts static?

 

The load tester I used is a heating element that puts a resistive load on that battery, it looks and smells like a toaster. The analyzer tests the battery and charging system while the engine is running, I have no idea how it works except that it probably measures battery resistance. That is why I ordered a new analyzer after learning that the load tester I used is outdated for computer cars. Great for the 442, maybe.
An analyzer costs more, but to me is a necessary tool with newer cars. I learned something today.
The battery always showed 12.8 volts with the key off, BTW. To me it was holding the charge as it should.

 

I meant the "dead battery" part.

 

A load test is done with the engine not running, the test confirms cold cranking amps and voltage static and unload

 

The electronic testers are the way to go in my opinion. They are more expensive but they also work with canbus systems to give you more accurate results if the alternator is working correctly. If you go to the auto part store to have it tested and they bring out the old school style ask if they can use the digital one. I think you guys are talking about the rectifier vs a diode?

 

same component, different name, slightly different function.
A Wheatsone bridge can have a bad diode and still function poorly. Or it can have a bad connection making for intermittent problems due to vibration.

A rectifier is a type of diode, a Wheatsone bridge is a rectifier made of 4 rectifier diodes.

​​​​​​​https://www.power-and-beyond.com/wha...iers-a-909411/

 

Sweet! Thank you