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2005 Jeep Wrangler won't start

Pretty sure this could be an issue with a dead battery, but thought I’d throw it out there for other ideas:

I tried starting my 2005 Jeep Wrangler yesterday and there wasn’t enough charge to get it started. I got a few slow revolutions and that was it. I gave it a jump and it started fine. Drove it for an hour or so and then went to restart it 3 hours after I shut it off and it was dead again. Another jump and I drove it for an hour (home). I was able to start it a few hours after that on its own, though it struggled to a bit.

Tried again this morning and it was dead from sitting overnight. A few other bits of info:

  • With the key in the ignition, the charge indicator is hovering just above 9V (it is a 12V battery) before I try to start it. When engine is running after start, it jumps to around 12V.
  • I am pretty sure I didn’t leave the lights on or door open overnight. I haven’t noticed the engine struggling to start leading up to the dead battery.
  • After I jumped it again this morning, it seems to be idling very low. In fact, the engine shutoff when I let it idle in neutral with my foot off the gas for a few seconds.
  • When I got in the Jeep this morning before trying to start it, it had enough charge for the radio and dashboard. When I turn on the lights/highbeams it struggled and the high beam indicator on the dashboard (blue light) was flashing.
  • Battery is not too old. I don’t have the receipt with me, but I think I bought a new one 3-4 years ago. The +/- connections are clean with no corrosion. I didn’t look too closely, but I didn’t notice any obvious connection issues from the battery leading into other components.

I’ll probably go buy another battery, but wanted to check with the experts out there to see if there is anything else I should be checking. If I do get another battery, would also appreciate any advice on things to check to make sure that is definitively the issue before draining it too.


Anything below 12.5 volts is considered a dead battery.

When a starting battery is deeply discharged, it can lose it’s ability to hold a charge.

Try replacing the battery.

Also, if you jump a dead battery and then allow the alternator to recharge the dead battery, you run the risk of frying the alternator.


More than likely a dead battery. 3-4 years is about all you get with some of these replacement batteries. It can be tested at the parts store.

You could have a bad battery, a bad alternator, and quite possibly both are bad. The output from the alternator should be 14V into an OK battery.

Your battery is obviously fully discharged, but it might not be dead. It has shown some ability to take a charge. An hour drive with a good alternator should recharge a good battery but that is not enough time to reach a full charge. A weak alternator won’t recharge the battery much at all.

Buy or borrow a 10 amp charger (a handy tool to own) and hook it up to the battery for 6 to 10 hours. Then check the battery voltage, it should be 12.5 to 13. Start the car, at a fast idle, 1,500 - 2000 rpm the voltage should be around 14.2. If the voltage is 12.5 or less the alternator is shot.

Whether or not the battery is shot depends how well it takes and holds a charge. After 10 hours on a 10 amp charger it should be fully charged. Once charged you have it load tested. If it passes the battery is most likely still good.

Bring it to a parts store for a free battery and alternator check. The in-car alternator test isn’t completely definitive, but they can usually diagnose completely failed units.

If the battery is 4 years old, probably just buying a new one is the most economical way to start. It might well fix the problem straight-away.

If the problem continues with the new battery …

  • Charge the battery with a battery charger to full charge, then load test it.
  • With a fully charged battery, measure the voltage at the battery terminals. It should measure very close to 12.5 volts. Now start the engine. The voltage at the battery terminals should measure between 13.5 and 15 volts. If not, you’ve got some kind of charging system problem.
  • If both of the above test ok, you may have a parasitic drain current in some circuit on the car which is draining the battery when the car isn’t being used. Check for any lights that remain on that shouldn’t, like in the trunk, glove box, engine compartment. Also the computers in the car can keep getting turned on which will discharge the battery. This happens if there’s a door switch that’s intermittent, that makes it seem a door is opening and closing. There’s an electrical current test a shop could do to test for a parasitic drain. The engine-off battery current shouldn’t measure much more than 50 ma once all the computers shut off.

Yours is a pretty common problem reported here. Most any well-recommended shop will be able to diagnose it for you without much trouble I expect. Best of luck.

Just to close the loop on this - it turns out it was the battery.

Thanks everyone for your helpful analysis. I learned a lot more about car batteries from it!

Good for you for getting to the bottom of it. Best of luck, and good driving.