bad alternator?

**98maro** · 03-02-2012, 10:39 PM

hello guys, i have a 00 grand cherokee, i ahd it for about a year no problems at all, but it just started messing up with me,
i was driving around 40mph when it almost dies for a min the odometer when up and down many warning lights came on, then it was running fine, then when i got to a stop sign the lights went off, the batt gauge went almost all the way down and then up.. all my gauges are going crazy! my guess is the alternator.. what you guys think?
right now is running fine..

i have a big sound system so i dont know if that messed up the alternator.. thanks for the help

i know its not a gm but i need help guys, i posted on jeep forums, over a 100 views with no response.lol

**FinZ28** · 03-03-2012, 05:04 AM

Best thing to do is take it to a local auto parts store and let them test it. If it turns out the alternator isn't the problem, you may have a bad ground somewhere, or some other electrical gremlin.

**98maro** · 03-03-2012, 10:38 AM

i was told another way to test the alt, is to disconnect the battery when the motor is running, i did that but everything worked fine, at the time i did that it was running fine, so im guessing its barely going south or what you guys think?
i was thinking it could be an electrical problem, i never had an issue with it.. could it be the pcm or something?

**KMdef9** · 03-03-2012, 02:39 PM

I would take it off and get it tested, it could be the regulator on it. Your battery may as well get tested too.

Your sound system can damage your alternator if your pushing a lot of juice.

**FinZ28** · 03-03-2012, 03:16 PM

Be careful about disconnecting the battery to test the alternator. That test was okay back in the day, but with all of the electronic systems in modern day vehicles, you don't want to short something out and end up with a bigger problem to deal with.

**flybird** · 03-03-2012, 07:54 PM

Since no ome had pointed this out yet, check you amp, make sure no wires are touching, (positive and neg)

I had this problem, my alt kept fluxuating and dropped significantly. Bat is new and alt was fine. Turned out the positive and negative on the capacitor were semi touching. Moved them apart, n everything was fine!

**chris1974** · 03-04-2012, 09:46 AM

Originally Posted by FinZ28

Be careful about disconnecting the battery to test the alternator. That test was okay back in the day, but with all of the electronic systems in modern day vehicles, you don't want to short something out and end up with a bigger problem to deal with.

^^This. Back in the day, you could disconnect the pos side of the batter, and if the Alt is bad, the car would die cuz it's not getting juice from anywhere. But I don't think I would do that on todays computer monitored engines.

I'm with Jon....I would probably start with the amp too. I had the same problem in my camaro a few years ago. Caused all kinds of things to happen. Is the SES light on?

**98maro** · 03-06-2012, 03:01 PM

Thanks for the tip guys in disconnecting the battery
I did not know that. And I'm sure I won't do it again,
I checked the sound system wires And everything seems fine.

Today the jeep just died on me.*
I tried to start it with Jumper cables. Seems that it wants to start. But it doesn't. I left the cables there for a while and still didn't Start.*
So I went to check the battery at autozone and the the battery is fine. 80% charged.*
But why is the jeep dead even with a good battery?

Electrical issue or alternator?

Thanks for reading & helping !

**KMdef9** · 03-06-2012, 03:06 PM

Do static draw test on it. Hook up an ammeter to the battery leads, it should be in the millamps iirc.

**FinZ28** · 03-06-2012, 04:07 PM

Check the battery with a volt meter when the engine is off. Check the battery again with the engine running. If the voltage drops once the engine is running, your alternator isn't working good.

**98maro** · 03-06-2012, 04:13 PM

The truck has no power at all. I mean no lights on. Or anything.
They tested the battery with the metter and seems to be fine.
What I'm thinking it could be One of the cables that run from the battery. Either positive or negative.
Bc only when we jump start it. It's when it wants to start.
Otherwise it's just dead.
I'm having so much hard time with this.

**FinZ28** · 03-06-2012, 04:30 PM

Originally Posted by 98maro:2753550

The truck has no power at all. I mean no lights on. Or anything.
They tested the battery with the metter and seems to be fine.
What I'm thinking it could be One of the cables that run from the battery. Either positive or negative.
Bc only when we jump start it. It's when it wants to start.
Otherwise it's just dead.
I'm having so much hard time with this.

I would think that you would have problems jumping the car off if you had bad battery cables. Still sounds like an alternator problem to me, anyhow. The alternator isn't charging the battery to full capacity, which is causing you to have problems driving it and starting it. The battery has to have enough juice to start the car to begin with, but it doesn't, which leads me to believe the alternator isn't doing its job keeping the battery charged when the engine is running. Did I miss it somewhere, or did you ever have the alternator tested?

**FinZ28** · 03-06-2012, 04:37 PM

Another thought, since it hasn't come up yet. Is there any corrosion on the battery terminals? If so, get some battery terminal cleaner and a wire brush and clean the corrosion off. This can cause all sorts of problems and is easily overlooked.

***SMWS6TA*** · 03-06-2012, 05:21 PM

also check the grounds, they sometimes get loose.

Now you audio equipment -

Did you do it or a shop?

Do you know where they ground the system?

Do you know where the in line fuse is?

Depending on how much amps they drawl you could be shorting the life on the OEM alternator and battery. Too much amp drawl and the system never fully recharges. Over time this kills both (battery & alternator).

If you know how much amps the system is drawling you can get a bigger alternator and or get a Capacitor

Capacitors at Crutchfield.com

Some systems that are big require them to be able to store up power from your battery and use during peak output.

If you had it installed and IF they were pros they should have inform you that you would need one.

**98maro** · 03-06-2012, 05:22 PM

i havent test the alternator yet, i will test it, but i want to make sure that is the last option, bc i think if the problem is the alternator the truck would still power because of the battery right? or a bad alternator can kill all the power on the truck?, now i went to put the battery back, it starts fine with no problem, so i dont know what the hell is killing the power and then after a while everything is normal?

**98maro** · 03-06-2012, 05:26 PM

Originally Posted by SMWS6TA

also check the grounds, they sometimes get loose.

Now you audio equipment -

Did you do it or a shop?

Do you know where they ground the system?

Do you know where the in line fuse is?

Depending on how much amps they drawl you could be shorting the life on the OEM alternator and battery. Too much amp drawl and the system never fully recharges. Over time this kills both (battery & alternator).

If you know how much amps the system is drawling you can get a bigger alternator and or get a Capacitor

Capacitors at Crutchfield.com

Some systems that are big require them to be able to store up power from your battery and use during peak output.

If you had it installed and IF they were pros they should have inform you that you would need one.

thanks scott, i did the work on the sound system, everything looks normal to me, fuse is fine, the red (power cable) is fine, all the connections are fine, but i noticed that right now the sound system is acting weird, it throws high bass when its on low volume, or the bass sounds funny, some times, never had this issue before. what could make the power go away and then comes back?

**98maro** · 03-06-2012, 05:30 PM

i have the capacitor but i never installed it lol

**FinZ28** · 03-06-2012, 05:34 PM

Go ahead and get the alternator tested. Some places can test it in the car, others can test it by itself. Regardless, you'll have peace of mind knowing where the problem is.

**KMdef9** · 03-06-2012, 05:39 PM

I'm willing to bet something is shoring out. Disconnect your audio equipment and run the jeep for a while and see if your battery goes dead again.

I still suggest a static draw test, if you have a digital multimeter or just and ammeter.

**98maro** · 03-06-2012, 05:56 PM

thanks guys, but the battery doesnt die, the battery is fine, there is something that is cutting off the power, but i have no clue what it could be,
i could test the alternator, but if its acting up all the time, when they test it is not gonna come up as defective or needs to be replaced,
im gonna test it with the static draw test, never done it before but im gonna find out a little bit more,

so what ill do next is take the sound system off and drive it, but i will never have trust on it again, i would rather sell it once i find out is fixed after i removed the system.

at this point is that nothing points to the alternator exactly, bc if it was already messed up i would not be able to drive it no where,,