TonyPa

Starting to get nervous. When I bought my 1998 Zj with the 5.9 weeks ago. He had to put a new battery in. He put a 825cca in it. Would not charge up he said. If you used a jump start. Fired right up. So he replaced the battery, it showed it was bad under a load test.

I have been using it daily sort of. And also checked with a digital meter just in case. When the Jeep is cold, charges fine. After warming up the motor. I noticed when I put the headlights on, and also sometimes the heater. When I stop at a redlight, or anywhere at idle. I'm dropping to 10 volts!! And everything gets dimm! Yike's

Soon as I hit the throttle it starts climbing back up towards 14 volts. After a little while!! The battery used to sit at 12.8 volts when shut off. Now it sits at about 12.0.

Now...I did see the alternator he put on last year, it is only a 90 amp???. That just seems small. I dunno much about amperage. But that's not what was stock.

My build sheet calls for a 150.amp. Although I only see 136amp available local to me. Is this alternator causing my issue? Makes sense, but im not good with electrical..

I see the battery cables when I pulled back some rubber sleeving has green crap in within the copper strands. They look tired....

Why when I am broke right after xmas..ugh!!




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dave1123

Cut the cable ends off and buy replacement clamps. Strip the ends back as much as you can without making them too short to connect to the battery. Clean the wire ends and the battery posts with baking soda and water mixed into a paste. Rub it in good with a brush and rinse it when it stops foaming. Do it again, until the copper is clean. Install the new ends and spray with a good corrosion protection after connecting to the battery.

OH....check under the battery for a small black button in the center of the tray. That's the battery temperature sensor. It tells the PCM to adjust the charging rate when the battery gets hot. It's important that it works.

TonyPa

Thanks. I'll do that today. I see he put some new heavy duty connectors on the battery. But where they do clamp onto the wire's look crummy.

That button under the battery, do I push it or something? I didn't know there was anything under there.

My buddy who is a terrible mechanic never even saw the vehicle said over the phone...I have serious issues. Maybe a computer? Like why stress me out??

I thought...cables, alternator...stuff like your stating.

TonyPa

Ohhh crap. I don't know if cables can truly cause an issue after warmed up. But I just snapped a photo before going to the dentist right now. I will mess with them when I get home.

These look pretty rough! The ONE hot one, shorter one, feels like its dangling from three threads.

Here's some photos. I hope its the cables...Cheaper fix. Than getting a alternator.

OF course mine does call for a 150amp, and I have a 90amp so I may change that later on.

But heres the photos!

dave1123

It's just a variable resistor that senses the temperature. It sends this reading to the PCM so the battery won't get cooked if it's getting hot. The problem is if it's reading hot when it's not, the alternator isn't putting out what it should to keep the battery charged. Most people don't even know it's there. It rarely doesn't work, but if the wires get corroded from battery acid it may not.

Corroded battery terminals are caused by acid vapors venting from around the posts because they are loose in the case. Pounding or twisting on the posts can break the seal around them and vent vapors. If you can get them clean, a little RTV silicone can be injected with a needle, if you can find a dopehead to let you use one. LOL! Superglue also works. It's always best to spread the terminal clamps or use a clamp puller when taking the clamps off.

dave1123

Those are nice clamps! They look like something for an electric forklift or golf cart. Why he stuck both wires in one setscrew hole is beyond me. The fat red wire is for the starter, the other smaller one is for everything else, like the feed to the fuse/relay box under the hood. The large black one is the engine ground, the smaller one is for the body. There are many small ground straps all over the place as well.

If your jeep has a rear window defogger, it should have a 136 amp alternator. Without the defogger, a 90 amp is enough, that is unless you start adding offroad lights or a kicking stereo amp or transmitter.

TonyPa

He thought putting on those custom clamps would fix it...he should have seen how terrible the wires looked!!! Should I separate them to each hole if possible? I don't know if that matters or not

Okay thank you. Will get on it this afternoon. I had to show a photo of the cables. Didn't realize they were that bad. I didn't know about the button underneath and what you meant by checking it. As in...pushing the button, or doing something to it.

dave1123

If you remove it, you can check it with an ohmmeter. At 75* to 80* it should read between 9,000 and 11,000 ohms, higher at lower temps.

To remove it, remove the battery from the tray, disconnect the harness plug underneath the tray, pry up on it and pull it out.

TonyPa

Crap....I didn't see the last post before I went into the garage. I snipped the ground cables, they were a bit loose inside the clamp. I put a new one on.

I could not snip back the hot cables wasn't enough slack. They appear to be green inside the center of them. But I did clean them up. New clamp.

Was a little better at first then the more it warms up and sits there and runs the worse it gets. It was sitting at 12.5 at idle with nothing running for except the engine. Under throttle, it only went to 13.5-13.7. It appears to do it more after warmed up. I am truly wondering if this advance auto 90 am alternator is crap. I put the battery on charge and took a break for an hour here

I read the regulator is,inside the ECM not in the alternator. I could be wrong...yikes!!!

dave1123

Yes it is, but it seldom goes bad. Usually it's in the wiring. You can take the alternator out and get it checked at an automotive electrical shop.

I was just thinking. If those battery clamps are aluminum, that's why they are corroded. Copper and aluminum don't get along in electrical circuits. There's what's known a galvanic corrosion. If you put a battery directly on the bottom of an aluminum boat, it will eat right thru the hull eventually. I've seen it happen!

Voltage improvement on warmup tells me to look at the temp sensor. Any time the engine is running, you should see 13.7 volts.

TonyPa

My voltage does not improve during warm up. Seems to get worse. I did charge my new battery back up tonight. It charged fast. I started the Jeep up and of course...perfect. But of course that was cheating. Because it didnt have time to run long enough to have the alternator or whatever not function enough to give the battery what it needed.

I changed those connectors to the old style tonight. I had some on hand.

Honestly i may change the 4 battery cables though. Im not saying its the problem, would be nice though. But when I cut them back Dave, the center core was green if that makes sense. I think these cables are tired. I dont know if that could cause a loss in charging after its warmed up or not. But these cables look like crap. I never seen any when you cut a fresh inch off of them and still see green color in the middle of the copper strands.

When I first start it it seems to go straight up to 14.2 then after operating temperature seems to start falling off. Hope its not my voltage regulator. That would make me sick. Right before I bought it. He had a scan done on it at advance and they ripped the slip off and handed it to him and told him everything was fine. I think that would have caught a bad voltage reg. Sorry, I googled and seen voltage regulator and it was in the computer and almost threw up.

TonyPa

Okay... change my 90 amp alternator to a, 136 amp. I did change my battery cables, and then slice open the rubber on it, they corrided extremely bad inside. Also I change them two other cables that go to the battery. Like one that a fuse box and one to the interwell. They were shot. Cleaned all my grounds everywhere. Now she's charging like brand new again. What a good feeling when you resolve something.

dave1123

Yup! That green corrosion on the copper has a very high resistance and will not pass power very well. With anything electrical, good clean connections are essential! Most people never pay attention to grounds. They look at them and assume they are good when they may not be.

TonyPa

You couldn't have put that any better. I should have took some photos just to put up, but I didn't think about it. My Jeep seems much happier now

wolfgrrrl

Yah know most of those bolt on terminal clamps are marked as emergency clamps not meant for permanent installation. I find the best when there is green inside the cable is to replace the cable with a factory or similar cable with the lead end. If you are going to use ones like in the pic tin the end of the cable with non acid solder and flux