Here we go again
 

I'm hoping someone can point me in the right direction, before I end up at the dealer.Back in late November I posted about flashing dash lights https://www.chevyhhr.net/forums/prob...-lights-61073/. I ended up replacing my battery, and that seemed to have solved my problem. We were away most of December so I didn't use the car.
A few days ago it started doing the same thing again with either flashing dash lights on start up, or no dash lights at all. I've been watching so many YouTube videos trying to diagnose the problem my head's about to explode! One thing I've noticed is my battery voltage reading without the motor running is showing 12.34, with the motor running 14.74, and with the motor not running and the battery terminals removed the battery is showing 12.70 volts. I'm wondering why the voltage is so different with the terminals on and with them off with the motor not running.
I'm also wondering if anyone can make any sense of my post.Any ideas would very much be appreciated

12.7 volts is a dead battery. 14.74 is the alternator output, that looks normal.

You could try charging the battery, sitting for a month can drain a battery.

What do you think a dealer could do that the guy down the street can't do?

12.7 volts is a dead battery?

If not exactly dead it is at 90%. 12.75V is fully charged. 12.0V is 20%. 12.34 is about 50%.
The 12.34 is because there are things using power when the key is off.

Then immediately after the starter draws the voltage may drop to critical level. Most of the computers need at least 9V to even boot, thus the flashing lights.

Where are you measuring? At the battery or at the large wire on the fuse box? The connection at the fuse box has been known to come loose or corrode.

Don, I'm measuring at the battery itself

I've checked and removed and cleaned every ground wire I could find. All were tight and didn't seem corroded at all.

I don't remember if we went through this before; load test is more than hooking up a VOM it actually puts a load on the battery to see how it responds.

Your description has all of the earmarks of a failing battery, new or not. Sitting for a month will draw a battery down. There are things like the security system and the Remote Control system drawing some. That will take more charging than a trickle charger or driving around a bit.

I'm taking it to a couple places tomorrow to have the battery and alternator tested. I'll let you know what the results are. I used it today to go to the grocery store, and everything worked perfectly.