Hi!

I just registered because my son's 2006 Cobalt SS won't start. He bought it before winter, used it a little (like a month), then parked it in the backyard and didn't start it since a while.

Of course the battery is now dead. I will replace it but I'm not sure this is the only problem: when I jump start the Cobalt with my 2020 Hyundai Elantra, the car starts quickly and everything is ok.

BUT if I unplug the Elantra battery and plug it into the Cobalt, then I can't even turn on the car (so of course I can't even 'try' to start). Looks like there's a short somewhere (maybe not, but it looks like there is).

My question for you guys who know the Cobalt very well, is: is it because of the type of battery the Cobalt SS uses? That would explain why it won't even turn on the car with my Elantra's battery?

Or is there something else I should look at before I replace the battery? I'm quite confused right now...

Thanks for your help!

(I'm attaching a piucture of my Elantra's battery, in case it helps...)

 

If its dying the alternator sounds to be out. It could be other things, as they were known to have lots of electrical gremlins. I would have the alternator tested first.

 

Thanks for your help. I think the alternator is ok, otherwise it wouldn't run fine after I jump start it, right? (The battery is dead so the alternator is the only source of power)

I guess I will replace the battery anyway then I'll see what's going on...

 

Where are you boosting from?
chwck to see if the lugs on the battery are corroded. Could explain why it won’t work with the Elantra bat but when you clip jumper cables to the outside of the cables it works.

 

I'm boosting from the battery lugs, there's no corrosion (not much).

Actually when the Elantra's battery is installed in the Cobalt, I can turn the ignition to the first position (so current is coming from Elantra's battery), instrument cluster is on, but when I turn the key to the second position then everything shut down, no power at all.

If I do the same thing while boosting the Cobalt from the Elantra, then I can go to first and second position without any problem, I can even start the engine and disconnect the jumper cables from the Elantra, and the car is running fine without any battery (like any car once it's started).

 

Very strange. Unless you have two weak batteries they only manage to start it together. What happens if you boos the Elantra battery with the cobalt batter while it’s out of the car? I assume it still works.
leaving it in the car all winter likely screwed the battery over to the point of no return.

 

I can't boost the Elantra's battery with the Cobalt since the Cobalt has no battery (100% dead). Elantra's battery is working fine.

I will have no choice but to replace the Cobalt battery and see what happens. I'll keep you up to date.

 

I'm assuming you verified the cobalt battery is dead by attempting a slow trickle recharge? (something like 2amp hour charge, not a rapid) Then tested the output voltage to confirm you had dead cells in the battery?

I'd be sure the lugs are tight, I had an issue with a lug loosening on a battery in the cobalt that would do exactly what you're describing. You could key to ignition on engine off and everything would be fine, then turn to start and everything would die. Verify the lugs into the battery are right and into the body for the ground is tight. Clean any corrosion from the terminal connectors, as any corrosion will have a larger effect on a weak battery.

 

Also, for future reference, the Cobalt should be jumped from under the hood. There's a positive lug that's part of the fuse box and the suggested negative connection is one of the nuts for the strut. This gives the jump a direct connection to the starter.

Jumping from the trunk connected to the battery makes it harder on the car and I believe there is a main power fuse that can pop if you do it that way too many times. Also, low power batteries will have more trouble starting the car from the trunk and being jumped in the trunk.

I would have the old battery tested and charged, unless it is more than a handful of years old (it likely is), in which case it is likely more trouble than it is worth. Fully discharging a battery tends to be quite harmful to its life expectancy.