My battery is being drained overnight so I did some checking with a dc amp meter between the neg post and disconnected grounds. I found a 260 mA parasitic draw. I think that's is way high. Fuse 26 labelled access.2 in the under hood pcm fuse box seems to be the culprit circuit. I pull that 10a fuse and get back to a 5 mA draw. Any idea of where to look for the problem or what that fuse is responsible for. I haven't done much homework on this yet but thought I'd see if anyone has a quick answer here.
2003 tj fuse 26 parasitic draw
- Thread starter benmack1
- Start date
A little more info, now I am not sure if I have a major draw or not. I measured the parasitic draw by 1) disconnect the ground cables from the neg batt terminal. 2) Place multimeter in DC amp mode in series to connect the ground cables to the neg batt terminal (so all the current has to run through the meter). 3) I immediately get 276 mA reading (that is way high) but that then goes down to ~4-5 mA after about 3-5 seconds. I initially was hung up on that 276 mA reading and ignored the fact that is went away quickly. Now I am wondering if this is 'normal' and just the computer waking up (because when I connect the meter it is like hooking up the batt again) then after a few seconds going back to sleep so my actual parasitic draw is only 4-5 mA? If so then the 276 mA isn't really my problem with my battery being dead.
More info, I thought my batt was shit so I replaced it with a new battery. It's an advance auto group 34/78. I installed it on Monday afternoon and didn't do anything other than start the jeep. I then drove to work tuesday (30 miles each way) and parked it in the garage Tuesday night. Wed AM, it went 'click' when I turned the key. The battery had 10.49V on it. The alternator was working on Monday when I put the meter on it after the batt install (getting 14.3V running). So WTF?
More info, I thought my batt was shit so I replaced it with a new battery. It's an advance auto group 34/78. I installed it on Monday afternoon and didn't do anything other than start the jeep. I then drove to work tuesday (30 miles each way) and parked it in the garage Tuesday night. Wed AM, it went 'click' when I turned the key. The battery had 10.49V on it. The alternator was working on Monday when I put the meter on it after the batt install (getting 14.3V running). So WTF?
3DCrawler
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Any thing over 70mA is to large of a draw. You really need to find a battery shunt so you don't totally lose connection when testing for a draw.
Skinny
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Wow, I was thinking like 15ma on a simple truck like a Jeep would be the upper limit. If you are going from 276 to 5 I'd say everything is OK. Typically it is just the computer shutting down after the key is off. If you disconnect and reconnect the negative with the key off you will get the same outcome. Computer sees power, sees everything is fine, goes back to bed. The way to avoid this is put the meter in place, then lift the terminal off so it never breaks contact.
Either way 5ma is not going to kill a battery. I would start back at the beginning knowing that you have a new and assumed good battery. Put the battery on a good trickle overnight to ensure it is at 100%. Then do a charging test. Can't accurately charge test without a known good battery. If you aren't seeing 13.5-14.5 roughly you may have a charging issue. Don't forget to check it no load and loaded at multiple rpms. Once that checks out, I'd say revisit parasitic draw.
Either way 5ma is not going to kill a battery. I would start back at the beginning knowing that you have a new and assumed good battery. Put the battery on a good trickle overnight to ensure it is at 100%. Then do a charging test. Can't accurately charge test without a known good battery. If you aren't seeing 13.5-14.5 roughly you may have a charging issue. Don't forget to check it no load and loaded at multiple rpms. Once that checks out, I'd say revisit parasitic draw.
Good point on connecting the meter then disconnecting the ground wire (or a shunt). I'll try that to pin this down further and make sure what I said is accurate. I've also got two of these TJ's and I was thinking I'll bring this new battery up to full charge (and make sure of it) then swap the two batteries and see if this one shits out in the other jeep or if I kill a second battery in the original jeep. Total PITA!
Skinny
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I like that idea. Being able to verify that you have a good battery is tough because lots of new batteries are junk. I'm assuming since it's new that it's clean but a physically dirty battery can drain.
Yep, I appreciate it and that's consistent with what I have read. I need to get my shit straight here and get the batt charged up and get some reliable numbers before I go all apeshit on assuming what's the problem. I suspect I have a very low parasitic draw (this is a bone stock wrangler, factory radio, no under hood light or dome lights (fuse pulled for those). Should be very little draw when everything is shut down. I am wondering after some reading if I have a fuct up alternator. It seems whatever this is has drawn a brand new battery down from full charge (assumed) to dead (10.49v) in 12 hrs. Even if I have a 'big' parasitic draw this would have to be massive to do that. I read diodes in the alt can fail and result in this type of battery decline overnight. In those situations I read that the alternator continues to charge when running it's just the backfeed from batt to alt with failed diodes that will kill the batt voltage when not running. Not real sure on this yet, just a thought while I am waiting to get time to properly dig into this.
More info I have thought of. I may have fuct myself on this, not sure. I redid my head lights back around Thanksgiving. I put in 2 relays to run the low and high beams to take the load off the factory switch and get full voltage to the lights. Now I just use the factory headlight H4 connectors to trigger the relay and all the current load is directly from the battery through the relays to the lamps. However, I didn't just route it directly from the battery, I used the alternator large hot lug which gave me the most convenient route to the relays to the lights (shortest route as well again thinking to keep my voltage drop to a minimum). I thought that just goes to the battery anyway so what's the harm. Maybe there is something in there I am not appreciating by hooking a head lamp load to this alternator lug that is causing a problem and I perhaps killed the diode(s)????? Minimally I'll re-route that back to the actual (+)ve post on the battery and at least remove that possibility. Or maybe this is unreleated.
I'll typically start with my power probe hook and supply ground to the ground cable over a period of two hours in the max/min feature. In the case I'm currently dealing with everything is in order but it'll still kill the battery I'll use my amp clamp and scope - (new batteries in amp clamp lol) and watch max and mins overnight. This eliminates changes caused by moving battery terminals etc. If I still have acceptable current draws I look at possible terminal issues. From my experience excessive current draw from alternators is usually consistent, I've seen very few that were intermittent in nature.
Skinny
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I agree, you would think a failing alternator causing draw would be all the time. I believe those vintage Chryslers are regulated via the engine ECM? Maybe it has lost its mind and tried fielding while the truck is off?
That would be a rare event from my experiences but anything possible. Typically that portion of the pcm isn't active until the ignition switch supplies power to the pcm. Anything is possible. It would be a quick one to pinpoint! Remove the alternator b+ and see if it still has issues!
Fully charged battery now. I left it unhooked all night (charged up yesterday). I had 12.7 v before I hooked it up. I reconnected everything, no big parasitic draw (just the <0.3A for the computer then settles to ~6 mA after a few seconds). I tried the starter and it started but died immediately. It fired just for a second or less I would say. Then I hit the key and it fired up and stayed running. I have 14.3V when running and all the accessories on. Seems the alt is putting out what it should. I shut it down, again no parasitic draw so it doesn't seem like the alt is drawing back after shutdown (bad diode idea seems like it is NOT my problem). I also did a diode test and it seems correct (put multimeter across the big post to the alt casing and I get nothing one way and a reading the other way).
So, how about the starter? I drove it for a couple minutes and parked it in the shed. After maybe 30 minutes I fired it again, and again it died right away. Then fired up OK after that. If the started is getting bad somehow, can that drain a battery quickly and kill it or not? Just trying to figure out which parts to pull off and take up to the auto store to test. Maybe I should take the starter? All I have is a multimter anything more sophisticated is beyond my equipment I guess.
So, how about the starter? I drove it for a couple minutes and parked it in the shed. After maybe 30 minutes I fired it again, and again it died right away. Then fired up OK after that. If the started is getting bad somehow, can that drain a battery quickly and kill it or not? Just trying to figure out which parts to pull off and take up to the auto store to test. Maybe I should take the starter? All I have is a multimter anything more sophisticated is beyond my equipment I guess.
If the starter was drawing that much amperage it'd likely melt the terminals. I'd vote that is another issue all together!
Well, after all this horseshit it looks like I got a bad new battery to replace my bad old battery. All my diagnostics above didn't make much sense because everything was fine. I believed I had a bad battery (was 8 1/2 years old) so I just replaced it with a new one from Advance Auto (34/78) without any diagnostics on the old one. Nothing special but damn the fawker should work for a couple years I assumed. So when it wasn't working after replacement I never thought it would be a bad battery 
. I took the starter off and had it checked, perfect. Then I took the whole damn jeep to the Advance store and everything checked OK he said but he then told me on an 800 CCA battery, his machine was reading 630 CCA's. OK, I don't know WTF that is supposed to read or if that is normal. After not knowing where to go next and some begging he said they could do a fast charge (35 min) with their charger and test just the battery. I think he thought I would bring it back later, I whipped a couple wrenches out of my pocket and followed him into the store. After standing around the store doing nothing for 35 minutes he did a batt test with his magic machine and voila, bad battery. 
Registered 653 CCA this time. Not sure why the first measurement didn't convince him it was fuct. So I got a new battery to replace my new battery. Going on 4 days now (fired up just fine today after sitting for 2 days). Hopefully this is the end of this particular drama. 
. I took the starter off and had it checked, perfect. Then I took the whole damn jeep to the Advance store and everything checked OK he said but he then told me on an 800 CCA battery, his machine was reading 630 CCA's. OK, I don't know WTF that is supposed to read or if that is normal. After not knowing where to go next and some begging he said they could do a fast charge (35 min) with their charger and test just the battery. I think he thought I would bring it back later, I whipped a couple wrenches out of my pocket and followed him into the store. After standing around the store doing nothing for 35 minutes he did a batt test with his magic machine and voila, bad battery. Registered 653 CCA this time. Not sure why the first measurement didn't convince him it was fuct. So I got a new battery to replace my new battery. Going on 4 days now (fired up just fine today after sitting for 2 days). Hopefully this is the end of this particular drama. Skinny
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Congrats dude!
I learned long ago never trust new parts until they prove worthy. Says my new wiper motor that squirts whenever the wiper motor is on...
They must have been using a resistive load tester to measure cranking amps and voltage drop. A more modern inductive tester would have sniffed out a dead/shorted cell pretty quickly. Either way, hope the new new batt works out for ya.
I learned long ago never trust new parts until they prove worthy. Says my new wiper motor that squirts whenever the wiper motor is on...
They must have been using a resistive load tester to measure cranking amps and voltage drop. A more modern inductive tester would have sniffed out a dead/shorted cell pretty quickly. Either way, hope the new new batt works out for ya.
I replaced almost every piece of my CJ's charging system once, only to find a corroded ground wire. Funny thing is, testing the ground wires for continuity was one of the first things I did. I guess they would move a few amps just fine, but not enough to charge the battery. I hate automotive electrical problems, but they can lead to you getting a good deal if you dont mind chasing wires after someone else has given up.
Skinny
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Continuity tests are good but for example, you have a ground that is slightly corroded. Continuity will show up pretty good since all you are asking it to do is pass the absolute tiny amount of current the DVOM is putting out to check resistance. We are talking near nothing. Now, same slightly corroded ground asked to say run enough current to light up a headlamp...you get a massive fail with a dim bulb. You've exceeded the corroded grounds ability to carry current.
That is where a good voltage drop test comes in. If you activate the circuit and measure for example from the ground side of the bulb to the ground point on the battery, you will see how many volts are dropped across the connection. In theory 0.1v drop is acceptable in most circuits (super high current stuff like winches you may get away with slightly more due to heat build up). So more than 0.1v dropped you have issues. So you work your way across the ground path. So if you had some goo on the ground post, you have the bad connection at the actual terminal point on top of the battery post. If you measure from the top of the post to the terminal, this is where you see the excessive voltage drop. All other points on the ground side would read good. A much better test for finding bad connections.
This test will also expose weak cables. For instance you have a failing positive cable going to your starter resulting in a slow crank. A resistance test will read good if only one little strand is left holding on for dear life. A voltage drop test would reveal a massive drop across that cable.
I hope that helps and isn't too confusing
Worst case just shoot the hostage!
That is where a good voltage drop test comes in. If you activate the circuit and measure for example from the ground side of the bulb to the ground point on the battery, you will see how many volts are dropped across the connection. In theory 0.1v drop is acceptable in most circuits (super high current stuff like winches you may get away with slightly more due to heat build up). So more than 0.1v dropped you have issues. So you work your way across the ground path. So if you had some goo on the ground post, you have the bad connection at the actual terminal point on top of the battery post. If you measure from the top of the post to the terminal, this is where you see the excessive voltage drop. All other points on the ground side would read good. A much better test for finding bad connections.
This test will also expose weak cables. For instance you have a failing positive cable going to your starter resulting in a slow crank. A resistance test will read good if only one little strand is left holding on for dear life. A voltage drop test would reveal a massive drop across that cable.
I hope that helps and isn't too confusing
Worst case just shoot the hostage!