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Is my alternator bad?

A

AntiFreze

Golden Member
So I was storing my 97 Jeep Grand Cherokee on the 9th floor of a parking garage in Phoenix. I've heard that the heat can kill a battery. The Jeep ran perfect before parking it the last time. Well I went to move it and it was dead, completely dead.

I pulled my car up and gave it a jump, and the Jeep started when I revved the car up. However, the jeep wouldn't stay running unless I kept my foot on the gas. If I left it to idle, the jeep would die.

Does this mean my alternator is bad? There were no signs when I was driving it... or could it be the battery?

 
A really dead battery can cause issues. Put the battery on an overnight charger in your garage and see if that solves things. The alternator light on the dashboard should be coming on if it's not charging correctly.

ZV
 
Yeah, charging the battery on a good overnight charger is essentially free and it has a good chance of fixing things. 🙂

Many modern cars cannot tolerate being left for more than a week or two without starting because of higher parasitic draw on the battery from all the electronics. I'm not surprised that your battery was dead after a month. If you plan on leaving the car sit for that long again, you're really better off to remove the battery and put it on a float charger.

ZV
 
Have someone keep slightly higher than idle RPM's (enough to keep it running) and disconnect the negative battery cable.
If it dies , it is the alternator. The car will continue to draw from the regulator of the alternator when the battery is disconnected
if it is functional.
 
Originally posted by: g8wayrebel
Have someone keep slightly higher than idle RPM's (enough to keep it running) and disconnect the negative battery cable.
If it dies , it is the alternator. The car will continue to draw from the regulator of the alternator when the battery is disconnected
if it is functional.
Click to expand...

That's not guaranteed, and, in modern cars, this test can cause problems for the computers. It is no longer recommended.

EDIT: If you need to test your battery and alternator, use a load tester like this one.

ZV
 
Well, my battery was still under warranty at Autozone. They hooked it up to give it a charge, and it told them to check the cables. I'm guessing the cellanoid was shot and wasnt even transferring the charge. I replaced it with a new one and it started right up.

I'll probably drive it once a week just to make sure it runs well.
 
I had this happen once, although it was cuz some asshat stole my freakin' battery and sliced up the serp belt, was pissed cuz it was snowing and I needed the car to get to work.
 
Originally posted by: AntiFreze
Well, my battery was still under warranty at Autozone. They hooked it up to give it a charge, and it told them to check the cables. I'm guessing the cellanoid was shot and wasnt even transferring the charge. I replaced it with a new one and it started right up.

I'll probably drive it once a week just to make sure it runs well.
Click to expand...

The solenoid is part of the starter. It will have no effect on keeping the engine running once it has been started.

ZV
 
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