2012 Not Starting Out of Nowhere

[quadzilla200]

I changed spark plugs last week. 155k miles. Drove fine yesterday. Turned the key today and got all the lights warning and a click, click, click from behind radio. Saw a service advancetrac warning for an instant. Set up to multimeter. Got an 11.95 no load. Turned key to start dropped to 7.9. Just a bad battery all of a sudden or something electrical?

 

[99WhiteC5Coupe]

I changed spark plugs last week. 155k miles. Drove fine yesterday. Turned the key today and got all the lights warning and a click, click, click from behind radio. Saw a service advancetrac warning for an instant. Set up to multimeter. Got an 11.95 no load. Turned key to start dropped to 7.9. Just a bad battery all of a sudden or something electrical?

Bad battery - and/or loose or corroded battery terminal connectors.

 

[Motorcity muscle]

Below 12v. is not good, I would trickle charge it overnight and re-test it. May have just left something on and drained it. Just went thru this with the back hatch window on mine.

 

[99WhiteC5Coupe]

I changed spark plugs last week. 155k miles. Drove fine yesterday. Turned the key today and got all the lights warning and a click, click, click from behind radio. Saw a service advancetrac warning for an instant. Set up to multimeter. Got an 11.95 no load. Turned key to start dropped to 7.9. Just a bad battery all of a sudden or something electrical?

What did you determine?

 

[Plati]

I changed spark plugs last week. 155k miles. Drove fine yesterday. Turned the key today and got all the lights warning and a click, click, click from behind radio. Saw a service advancetrac warning for an instant. Set up to multimeter. Got an 11.95 no load. Turned key to start dropped to 7.9. Just a bad battery all of a sudden or something electrical?

Many times I have done some maintenance and my sharp elbows and clumsy hands have knocked something loose or out of position. Could be that. Also ... many times a new problem pops up that has nothing to do with the last thing that happened which is confusing to diagnose. I would say take it one step at a time ... look for things knocked loose, fully charge battery and verify battery and charging is ok then ???

Here's my battery / charging health check. Fully charge battery, should go up to 13.5V or so. After 12 hours with no activity CAN drop back to 12.4V or so (resting, engine not running). Measure battery voltage while you start engine, can drop to 10V or so momentarily but then when started the charging should kick it up to 14.5V or so while running. Turn on all the fans and lights and it should be able to handle that with no voltage drop. Numbers are approximate and variable depending on system under test.

 

[Motorcity muscle]

Did you figure it out?