Come on guys, we all know test lights and DVOM each have their place. Let’s wait for a picture of his battery and cables. Hopefully they just need a good cleaning.
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- Thread starter yummycurryboy
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I'll just say that I appreciate the help from both of y'all.
I took the battery to Napa and it was only reading 5 volts. I left it there to charge overnight. I have scrubbed the terminals and the copper contacts clean with a wire brush. If tomorrow I find out the battery is the issue, I should be able to have it replaced under warranty. IF the battery is not the issue I would guess the alternator is bad or the contacts were preventing the alternator from properly charging the battery.
I'll do some testing once I find out the status of the battery.
I took the battery to Napa and it was only reading 5 volts. I left it there to charge overnight. I have scrubbed the terminals and the copper contacts clean with a wire brush. If tomorrow I find out the battery is the issue, I should be able to have it replaced under warranty. IF the battery is not the issue I would guess the alternator is bad or the contacts were preventing the alternator from properly charging the battery.
I'll do some testing once I find out the status of the battery.
I forgot to take a photo but I can assure you all that, after an hour with a wire brush, the contacts are definitely clean now.
Good to know. Hope it’s an easy fix and all you have to do is replace the battery. Do you have a spare battery you can throw in to check it out?
I could probably pull the battery out of my girlfriends Jeep Patriot, assuming it is compatible, but I am fine just waiting until tomorrow. I am in no rush to get the Jeep running again.
So I put the charged battery in and she started right up. I ran her for about 10 minutes with no issues. The dash read 14 volts the whole time. I guess my alternator could be bad which caused the battery to deplete over time. What is the best way to trouble shoot an alternator?
With a meter.
If you reading 14v there, I bet you are ok. You need a meter to check the alternator. I’m inclined to think you might have a drain on the system you’ve not seen. Do you have fog lights? If so, are they turned on/off with turn signal stalk? If they are, every time you get out of the Jeep. Look back to see if they are on. This is a common issue and can be easily fixed.
Yea, I was thinking about what could be draining the battery. I have a switch on the dash for the fog lights. I generally keep them off. I don't think I left anything on the particular night it got drained but I can't be sure.
I have aftermarket LED headlights and an aftermarket head unit. But I have had them in for months with no issues.
One strange idea that came into my mind was that the day before the dead battery I sprayed some WD-40 penetrating oil on the tailgate hinges (they have been squeaking). Because of the proximity, some of the oil may have gotten into the right rear taillight. Could that have caused some sort of electrical issue?
I agree. You need a meter at this point. If you configure your meter in Amps, disconnect the negative battery cable, touch or clamp one probe on the terminal, and the other probe to the cable so the meter is connected in series. You should read zero amps with the key off. Even 200 milliamps can drain the battery if it sits long enough.
If you do have a reading, you can first make sure all of your switches are off like Ericict said, but then you'll start pulling fuses one at a time while watching your meter. When you pull the right fuse, your meter will drop to zero. You'll then know where your problem is, based on the fuse pulled. I'd start by pulling the wire off the stud of the alternator. I've seen multiple vehicles that charge just fine, but a bad diode in the alternator causes it to drain when turned off.
To visually see how this works, you can also connect the meter up in series as described above, and then turn your headlights on with the key off and watch your meter. The Amps reading will jump.
** Also, when testing parasitic draw, I can't stress enough that it should be on the ground side. You can accomplish the same task by setting the meter up on the positive side, but if one of your probes, or cables moves, or your meter falls, you can have a massive short to ground. If you perform it on the ground side of the battery and the meter slips, you're already on the ground side... so, no sparks, no short**
If you do have a reading, you can first make sure all of your switches are off like Ericict said, but then you'll start pulling fuses one at a time while watching your meter. When you pull the right fuse, your meter will drop to zero. You'll then know where your problem is, based on the fuse pulled. I'd start by pulling the wire off the stud of the alternator. I've seen multiple vehicles that charge just fine, but a bad diode in the alternator causes it to drain when turned off.
To visually see how this works, you can also connect the meter up in series as described above, and then turn your headlights on with the key off and watch your meter. The Amps reading will jump.
** Also, when testing parasitic draw, I can't stress enough that it should be on the ground side. You can accomplish the same task by setting the meter up on the positive side, but if one of your probes, or cables moves, or your meter falls, you can have a massive short to ground. If you perform it on the ground side of the battery and the meter slips, you're already on the ground side... so, no sparks, no short**
I didn't make it perfectly clear, sooo... by "pulling your fuses one at a time" I mean, pull the fuse. If nothing changes on your meter, put the fuse back in, and move to the next. I could see someone following my instructions above and at the end having a pile of fuses 
that would suck!
that would suck!
That makes good, clear sense, I just ordered a multimeter so I can do this. Thank you for this write up!
Three points:
1. What would you do if there is no reading on the initial check? Call it a fluke? Assume that on the particular night the battery died I left something on by mistake?
2. Should I just be checking the fuses in the box behind the glove box? Should I check the relays that are in the box located in the engine bay?
3. I have had this Jeep for nearly two years now. Is it really likely that all of a sudden the battery is being drained after having no drainage issues with the battery in the past two years of ownership? I used to own a 1986 BMW 3-series E30 and the electronics on that car were more temperamental than any girl I have dated. On the contrary, I've always though of TJ's being relatively straightforward and reliable with the electronics.
Question 1: If your reading is zero, it's very possible something was left on. We're human, it happens. Could've been a glove box light or under hood light that stuck on, etc. If it is zero, parasitic draw is not the reason your battery failed. Could've been a bad cell, the vehicle sat for a long time, or any number of things.
Question 2: Pull all fuses under hood and in the glove box one by one (like I said though, if your meter shows that there's an amp draw, start with pulling the battery cable from the stud of the alternator. Alternators are often guilty of parasitic draw caused by bad diodes). Pulling relays would accomplish the same thing as pulling fuses. Understand that all you're doing is creating an open circuit (shutting that particular circuit off) when a fuse or relay is pulled to see if that particular circuit is the culprit of the parasitic draw. That being said, all of the fuses that you will pull are before power reaches the control side or load side of the relay. The problem with pulling relays to look for an amp drop, is that there are a minimum two circuits involved with a relay. It won't necessarily be as obvious what the problem is to someone who's newer at this stuff.
Question 3: It's absolutely likely that all of the sudden this could happen. That's kind of how failing components work. One day they're working great, and the next they're draining your damn battery. Don't over think that portion of it. This is the beauty of troubleshooting. It takes the guesswork and the blindly throwing of parts and money out of the equation. Your mulit-meter will show you without a doubt, what's causing the issue. Also keep in mind that if your Jeep sits for looooooong periods of time, even the smallest of parasitic draws will eventually drain your battery. It's best to start your vehicle every once in a while to protect against this, or keep that battery on a trickle charger.
There's a specific way to set up your multi-meter for Amps, Voltage, and continuity/ohms. I won't bore you with written instructions. There's too many good videos online you can watch on how to set that up. But please.... please don't attempt to start the vehicle with your meter hooked up in series while looking for Amps. That'd be a really cool way to let the smoke out of your brand new meter! We're just pulling fuses here.
Keep me posted!
Question 2: Pull all fuses under hood and in the glove box one by one (like I said though, if your meter shows that there's an amp draw, start with pulling the battery cable from the stud of the alternator. Alternators are often guilty of parasitic draw caused by bad diodes). Pulling relays would accomplish the same thing as pulling fuses. Understand that all you're doing is creating an open circuit (shutting that particular circuit off) when a fuse or relay is pulled to see if that particular circuit is the culprit of the parasitic draw. That being said, all of the fuses that you will pull are before power reaches the control side or load side of the relay. The problem with pulling relays to look for an amp drop, is that there are a minimum two circuits involved with a relay. It won't necessarily be as obvious what the problem is to someone who's newer at this stuff.
Question 3: It's absolutely likely that all of the sudden this could happen. That's kind of how failing components work. One day they're working great, and the next they're draining your damn battery
. Don't over think that portion of it. This is the beauty of troubleshooting. It takes the guesswork and the blindly throwing of parts and money out of the equation. Your mulit-meter will show you without a doubt, what's causing the issue. Also keep in mind that if your Jeep sits for looooooong periods of time, even the smallest of parasitic draws will eventually drain your battery. It's best to start your vehicle every once in a while to protect against this, or keep that battery on a trickle charger.There's a specific way to set up your multi-meter for Amps, Voltage, and continuity/ohms. I won't bore you with written instructions. There's too many good videos online you can watch on how to set that up. But please.... please don't attempt to start the vehicle with your meter hooked up in series while looking for Amps. That'd be a really cool way to let the smoke out of your brand new meter! We're just pulling fuses here.
Keep me posted!
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