Is my alternator bad?

Question

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.

Answer 1

Right now you're in the assumption stage aren't you?  The car isn't running so you're assuming.  I would rather make the assumption that the car has a completely dead battery and when you put your foot on the gas, the alternator pumps enough juice into the battery so it will work.  You seem to think the alternator is an independent entity.  The alternator only puts juice into the battery.

Answer 2

If it runs with your foot on the gas, it's probably not the alternator.  You never said how long it was in storage.  It could be a number of unrelated problems.  Air in the fuel lines... water in the fuel lines... An ignition issue... Engine Control Module (ECM) issues...  Injector issues...

If the battery is toast it could be pulling down the alternator.

Replace the battery...  then go from there.

Answer 3

First, DO NOT disconnect a battery cable when the car is running. This used to be a good quick and dirty test back in the day. Now, you will surly blow out some electronics if you do that.

Next, find someone with a simple volt meter if you don't have one yourself, get the car started even if you have to hold the peddle down to keep it running. Put the volt meter across you battery terminals. If it reads 13.5 volts or more your alternator is fine.

Answer 4

Ya most likely i just got done changing my alternator on my 99 F150. It kinda did the same thing. What it really sounded like was that it was running out of gas or something like starting to idle really low and it just stopped eventually. Lucky i was close to home lol so i could coast down the hill. But i would also look at the belt and make sure it didnt get chewed up by the alternator. And maybe test the battery cuz it could be dead as well.

Answer 5

Sounds like your alternator is done...I had the same problem before, but I had both my battery and alternator replaced.

Answer 6

you probablu have a dead battery, and POSSIBLE a weak alternator, an easy way to test it is get it running, and disconnect the negative battery cable from the battery if it dies right away, you have a bad alternator...

But it sounds like the battery

Answer 7

if it dies when it is idling, then it,s probably the alternator. even if the battery is dead and once you get it started it should run off the alternator until the battery gets charged.