2000 Cherokee sport 4.0L 168000 miles

I drive to work ok. Come out and it just clicks. Get a jump. It starts. Runs really rough, gauges jumping all over the place, windshield wipers coming on etc... I make it almost home and smoke starts pouring out of the dash. Had it towed to a buddies shop. He checks and it's putting out 19volts. None of the dash gauges are working. His prognosis is that the battery is dead (as it's sitting in the shop there is a loud pop and the top of my Optima battery flies off.). It may be the alternator and/or the PCM module. He can't program the PCM so it has to go to the dealership and he had no way to tell what else might be fried.

So here are my questions for the group.

Is it worth fixing? With the over voltage, what else could be fried ( my buddy mentioned that it wasn't shifting properly when he put it on the hoist) Will the dealership be able to tell by plugging in what else is damaged or will they have to test each system? i thought there were fuses so this kind of thing doesn't happen!

Thanks

Geoff in Wisconsin

 

Fuses react to amperage, not voltage, battery exploded huh? cool.

 

Hey Geoff, welcome to the forum. Sorry it's because of this issue! It could be that the battery is faulty. If its off to a dealership then you'll have to wait and see what they say, but in the mean time your doing the right thing- research! Idk if theres any recalls on your battery, I doubt it, but I'm runnin low on ideas..

 

IMO a faulty battery isn't going to suddenly develop a 19 volt surge and fry everything in the dash. Sounds more like a faulty alternator than a battery. The alternator is what feeds the battery its charge, if the battery is dead, your 19 volts is coming from the alternator.

 

Good call.

 

Alternator or PCM, or both. I assume the regulator is still in the PCM that year?
Most of the "big" electronics, TCU, ECU etc have some rudimentary overvoltage protection built in. Generally a zener diode or varistor that crowbars the input when voltage levels climb too high. That can stop the module from working right until the voltage level drops again, but it's (supposed to be) a temporary protective shutdown. Hopefully any residual damage is limited. No real way to tell without applying 12V to the system and seeing what doesn't work.

I had a similar event on DW's Impala, smoke filled the car... the only permanent damage was to the multifunction switch (and the alternator that caused it) Hopefully your experience will be similar.

 

I wonder why it needed a jump in the first place. Any chance the cables got attached backwards..even for a second? I wonder if the PCM would drive up the voltage if it, it's self was seeing low voltage. I myself, (after ricing the acid and applying a box or two of baking soda anywhere the acid might have gotten), I might install a new battery, then start looking at things with the belt off, or loose and try to get a handle on it from there. Maybe starting with seeing what the PCM is telling the alternator to do. Get the codes read. Just throwing out ideas! Mine is not as complicated as yours. Sorry Btw,,,It get's better from here I'd think!

Btw....one time my Celica wipers came on when a hot shorted wire burnt through the insulation and energized the power to the wipers. Also a guy recently had a issue with one injector getting constant power, after hooking up jumper cables backwards. I bet some melted wires will be found under the casing on some harness somewhere.

 

This sounds very similar to the issues I'm having with my 2001 Cherokee limited. My voltage spikes constantly and my gauges are tweaking out occasionally. Exmple: today my alternator was overloading my battery and all of my gauges were freezing up or going down to nothing, while I was driving. Now mind you I've already replaced all my positive cables, the alternator and the PCM but the vehicle continue to do this. I did however get the problem to replicate itself by grabbing the wire harness and pulling on it. I watched as my analoge voltage reader went from over 19v to a steady 14v when the harness was tight and rigid. The moment I gave the harness slack it climbed back up over 19v. So somewhere in the secondary harness are bad wires. Perhaps that is where your problem is but if anybody has a spare harness or knows where I can get one please let me know

Ps- my jeep was running at idle when I was messing with the wire harness