bnelson1980@gmail.com

Hello,

I’m new to the forum. So I have a 2000 Jeep Grand Cherokee with V8. I only drive it a couple times every other week. Started having issues with it not starting a couple weeks ago. I went and purchased a new battery and that fixed it, so I thought. Then it wouldn’t start again. I jumped it and it ran, I drove it around and when I got home I turned it off and could not get it started again. I checked the alternator with my voltmeter and got 13.8V even with the AC on. Tonight I went and bought a new alternator because I read somewhere it has to be in the 14’s volt. I installed the new alternator. Jumped it, drove it about 10 miles and came home. Turned it off. Started it back up. Turned it off again and let it sit for a minute. Went to start it and it wouldn’t start. Any ideas what else it could be? I appreciate any help. Thank you.

BlueRidgeMark

Welcome to the forum.

Well, now that you've fired the parts cannon and missed, let's try some diagnosis. But first, a couple of admin notes.

1. Wrong forum. Grand Cherokees have their own special place. I'll report your post and a moderator will move it to the correct spot. No problemo. For your reference, that's here.
2. NOT a good idea to use your email address as your username. It invites spam. Here's why. I suggest you ask a moderator to change it for you.

Now, you ain't charging. You have a voltage regulator that controls that. IIRC, on yours it's in the PCM (Powertrain Control Module), the computer that runs the engine. If that has a problem, you can buy a bazillion new batteries and alternators and it isn't going to help.

First thing to do is the basics: check ALL of your battery and alternator connections. Don't just look at them. Take them apart, clean them. You want shiny bare metal, and reassemble with some dielectric grease. This prevents corrosion.

Now, what about the cables? They can be corroded inside the jacket. You need to give them a stress test. Push, pull, shove, yank. If it's bad, you WANT to break it, so you know what to fix. Feel them as you bend them - do they bend smoothly or do they feel 'crackly'? That's corrosion breaking up. Replace the cable.

There's your action plan. Do that and pop back with any questions.

bnelson1980@gmail.com

I was worried it would be the PCM. I’ve checked and cleaned all the connections. I’m going to take the battery in to have it tested.

how do I contact a moderator to change my username?

dave1123

You need to check the condition of the battery temperature sensor underneath the battery. It's purpose is to tell the PCM when the battery is getting hot, to cut back the charge rate. It may be sending a hot signal all the time so the alternator isn't doing it's job. Also, if the starter is pulling too many amps because of poor connections, the cranking voltage may be low enough for the PCM to not function properly. You may also have a parasitic draw, that is something that's pulling the battery down after you shut the engine off and over a period of time, reduces the battery charge. A fully charged battery should be at about 12.5 to 12.75 volts. A battery that's 12.0 volts is 1/2 dead. At 11 volts, it won't even crank the engine over fast enough for it to fire. When it's running, system voltage should be somewhere around 13.5 volts and drop down to 13 when the battery is fully charged.

After you shut the engine down and leave the vehicle, it takes about 20 minutes or so for all the modules to go to sleep. After that time, the only thing drawing power is the radio and PCM memory which is around 0.75 milliamps, if I remember correctly. If you have the alarm set or have a remote start system, it will be more. Anything that's active will draw down the battery over a period of time. One of the biggest things that cause a battery to go dead quickly is an aftermarket radio with an amplifier that doesn't turn off because of a wiring issue. If a glove box light or underhood light is on is another problem, especially the dome light because the body control module is still active then. If the vehicle will be stored for a long period of time, it's best to disconnect the battery and install a trickle charger on it or remove it from the vehicle.

About changing you username, send a private message to a moderator, usually listed at the bottom of the main page for that day, or Outlaw Star who is an administrator.

bnelson1980@gmail.com

I took the battery out and brought it back to the store. They put it on their charger and then tested it. Came back that the battery was unable to hold a charge. They gave me a new replacement battery and all is good now. I've never had a battery go bad after only a month. I learned a valuable lesson. Just because something is new doesn't mean it's not the problem.

dave1123

You will find that same thing with aftermarket sensors all the time. Also, beware of Dorman for anything that can't be changed quickly because you will if it fits in the first place!

BlueRidgeMark

Yeah, that bites a lot of us.

Glad you got it sorted out!