dead voltage regulator?

I was out of the country for a few weeks and when I got back, we've had some
sub zero temps.. combined with my alarm this discharged my battery to the point that nothing comes on on my truck.

so anyway, I grab my other vehicle, hook up the cables, let it charge for a few minutes and fire it up, It fires up right away without issues. Now, when disconnecting the cables I accidentally touched them together, shorting my heep out. Just a quick spark -.. however, truck dies instantly. Sure enough, no start again. So I hooked the cables back up, and after a few minutes of cranking slowly and whatnot it fires back up again..but wont idle..soon as as I let the gas out it dies. Got it up, held the gas on for about 20-30 seconds and it idles again.. ok fine..everything seems normal.

Let it idle for about 15 minutes and I take off to go get some gas. about 3 blocks later I get a 'check gauges' and the voltage is pinned at 19v (the top).. this worries me of course but nothing seemed affected. about 30 seconds later all power dies and I coast to the side of the road...no power, nothing. I didn't have a multimeter with me but my secondary accessories (IE rock lights) don't turn on and those have nothing to do with ECU or anything like that so I'm suspecting the battery is dead still, after 15 mins I would have suspected it would have charged enough to do SOMETHING.. the wife said my brake controller lit up when I was monkeying around with the battery but that was the only sign.

So.. dead alt? dead batt? Both? anything else I should check? I'll probably go back there with another battery and see what happens but in the mean time, ideas?

i'm gonna be pissed but feeling stupid if I fried something by doing something as stupid as touching the cables together like a newbie

Sounds like what I have been having issues with ( minus the 19v as I get 0v ) These single digit temps are no fun. Go through my thread and see if you get any answers.

Yep I did that.. first things first I Think i'm going to drop my other optima in and see if I can get er home at least heh.. that'll be later tonight though as i'm out today.

FYI it's a yellow top in there now but ya, drained right empty so it could be toast. Luckily I only paid 80 bucks for it as remanufactured/certified.

Ok, stop trying to run the vehicle on that battery.

Pull it, fully charge it, and have it load tested. If that battery is still any good at all, it is so discharged that you will never charge it by jump starting the vehicle--the voltage available while running the engine will be too low to excite the alternator for charging.

10-4 will do. Would jumping it and running it cause the results I had? IE 19v check gauges, then no power/dead?

Well, the available voltage with the engine running is probably below the threshold for operating the PCM, anything below 9 volts and everything goes wonky.

Once the battery is charged test the voltage to see if its charging correctly, post up what you find.

sent you a pm joe. need your help bud

Alright, so I pulled the red top out of my samurai and tested it, it was low too at about 10.5 cold out of the truck. I tested the yellow top in the heep after I got back to it and it was at 6..super low way too low. put the red top in, jumped it and it's good.. let it idle for quite some time to charge up and bring things up. Tested running voltage and it's 14.5 as it's supposed to be.

got the yellow on the charger now and it's charging. will check it out tomorrow.

One of the odd things about some electronic engine systems, and especially about Chrysler, is that they will work very badly with a bad battery. It's not necessarily low voltage that will do it (though they'll also drop dead at around 9 volts), but high as well. A good battery acts as a filter for the chopped DC that an alternator puts out, and when the battery is so dead that it won't accept a charge, the electronics get the unfiltered DC.

Lose the Red top. Hear about this porblem all the time.
Can't jump have to pull and charge battery to get it to run.
IMO way to much of a PIA for a few extra amp. With most bats you would have jumped it given it 15 min if compltly drained and been on your way. NOT with a red top.

Matthew Currie said:

One of the odd things about some electronic engine systems, and especially about Chrysler, is that they will work very badly with a bad battery. It's not necessarily low voltage that will do it (though they'll also drop dead at around 9 volts), but high as well. A good battery acts as a filter for the chopped DC that an alternator puts out, and when the battery is so dead that it won't accept a charge, the electronics get the unfiltered DC.

Click to expand...

Very true. He did also mention that it was a dead battery in sub-zero weather. A dead battery can freeze and break the plates or otherwise become ruined. A broken plate would also explain the high voltage reading as the battery basically wasn't there to regulate and smooth out the alternater output.

Well it's working ok right now with the borrowed red top... the yellow top is at home on the charger right now so we'll see how it's looking when I get home.

This morning it was having a hard time idling but it started on it's own and after a minute of holding it above idle it was fine. Just went out for lunch and had no problems

So an update.. I had to jump my truck this morning after leaving it all weekend.. it cranked but was super slow..

While I was doing it however, I noticed a symptom for my OTHER issue - my goofy idle issue. My #1 plug was arcing out on the head! when it arc'd the truck would idle like shat, then it stopped arcing and idled fine.. <slap head> off to the parts store.. got new wires and it idles perfectly fine now.

That being said - is it possible that THIS electrical issue has anything to do with my charging electrical issue?

Ok, toss a volt meter between the battery terminals and start the engine--should read 13.0 to 15.3 volts, if not it isn't charging.

What year XJ? We never did go over the BASICS of your rig--year/engine/etc.

I tested it while running and it was at 14.5 or so..

It's a 98 4L. I'll put my yellow top back in which was on 10amp charge for 24 hours and has been chillin on 2amp since then.. when I get home that is.