OK, replaced the alternator for a new one and a new battery. The hhr ran perfectly, after running for about 2 hours or so and shutting it off for about 5 minutes the hhr struggled to turn on. When driving it feels like limp mode and the lights flicker quite a bit. After a few hours if I try turn on the car it will turn on fine. Once it warms up and i shut it off it runs like its drained...I'm more confused with this issue???

 

Could be the positive connection at the starter, or a ground.

 

Is the Check Engine Light on? If so, you need to download the codes with an OBDII code reader and post the code itself here.

Otherwise, it's time to take it to a shop for a proper diagnosis, before you throw more money into it without resolving anything, or cause further damage. The electrical system in the HHR is not simple like the cars of years ago.

 

Are you checking the charging system after replacing the parts ?
Sounds like it's still not charging and it's just running till the battery drains down.
Can't just throw parts at it without checking to make sure they're working.

 

Whopper, the check engine light isn't on but the dashboard does say low voltage.

 

so the battery light is on I'm assuming..... Get them tested at local parts store. Then check grounds and connections to whatever part fails the test. If that doesn't work replace the failed part. Done!

 

I am betting on a loose wire somewhere. You need to find out if the alternator is putting out and just not getting to the battery, or if it is not functioning for some reason. Like the control wires are broken.

All of the ground locations under the hood. https://www.chevyhhr.net/forums/how-...cations-56504/

You might check fuse #16 on the BCM.

Did somebody throw the current sensor near the battery away, thinking it was just a piece of extra stuff? It is on the negative cable at the battery.