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Discussion Starter · #1 · (Edited)
Hi All,

Title says it all. I had a battery installed by Nissan Dealer in July 2016 and over the past week it's been starting slow. I checked the alternator, 14.7 volts at the posts. The other day, wouldn't start but I was ready and had a jumper pack with me so was able to get going. I drove it to an Advance Auto and they did a battery test. Saw that it needed replacing. The battery isn't even 2 years old yet and since the dealer is closed till tomorrow I thought I check for other issues.

I pulled the negative cable off the post and put my DMM in series. With all the doors shut, no lights, key in off, etc it's pulling 5A! I pulled all of the fuses in both engine compartment boxes and the fuse panel behind the glove box. Still there.

What's going on here? Most recent changes is a month ago I installed a DVD double-din head unit (but I thought of that and pulled the whole thing out and the amp draw was still there). I also installed a new timing chain and installed a new alternator when I did it but that was in November 2017 (4 months ago) so I don't think either of those things are the cause.

I made sure my DMM was in Amps and not Milliamps.

The only way I can get the draw to stop is by removing two cables from the positive battery terminal. When looking at the batter from the front of the engine compartment. The lead on the right side of the plastic terminal gang and the gray plug on the back of it on the right side. With EITHER of those connected I still get the amp draw. I'm just not 100% sure where they go or what they have in common.

Stumped...

Thoughts? Also, what's the accepted draw on this for a target? 50 mAmps?
 

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After it goes fully asleep, don't touch anything in an hour, less than 5mA is to be expected. But 5A when off is way too much. That's about 60W of energy that has to be dissipated, the heat of a 60W light bulb.

New alternator? I don't trust new parts. 5A could be the excitation coil staying on. Unplug the alternator and see if that is it. Next try unbolting the big charge wire, you may have lost a diode in the alternator.

Aftermarket stereo, amps have been known to go bad and get stuck "on". Just because you unplugged the head unit doesn't mean you disconnected the amps.
 

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Discussion Starter · #3 · (Edited)
After it goes fully asleep, don't touch anything in an hour, less than 5mA is to be expected. But 5A when off is way too much. That's about 60W of energy that has to be dissipated, the heat of a 60W light bulb.

New alternator? I don't trust new parts. 5A could be the excitation coil staying on. Unplug the alternator and see if that is it. Next try unbolting the big charge wire, you may have lost a diode in the alternator.

Aftermarket stereo, amps have been known to go bad and get stuck "on". Just because you unplugged the head unit doesn't mean you disconnected the amps.

No amp included. Just swapped out the original OEM CD/Radio player with a JVC V830BT so I could finally be cool and talk on the phone loud enough that my conversation could be heard two lanes over.

I also installed new speakers (forgot to mention that). I bought everything from Crutchfield and they built wiring harness adapters for everything, it was all plug 'n play, so I doubt that's it (plus I unplugged the head unit and removed their wiring harness when doing the test). I don't know if speakers by themselves could pull 5.0A, plus they get their juice from the head unit (or external amp if in play) which I had unplugged.

For the alternator - it has a wire that goes to the positive battery post which sits under the plastic gang that has the hot leads going to the fuse boxes - correct? I pulled that off and did a test which still showed 5.0A draw. You think I need to get under the truck and yank it out?

When you say the vehicle "goes to sleep" how does that work? When I hook the DMM in series on the ground, it's like connecting the battery terminal to the post. So the car "wakes up." If everything is installed I can hear the head unit booting up, working the DVD header/eject mechanisms, and the HVAC cycling. After that it goes silent. My DMM only lasts about 3m 45s at 5A before it kicks into OL protection. Disconnecting it kills the car. How can I do this test after letting the car sit for an hour without completing the electric system circuits?
 

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For the alternator - it has a wire that goes to the positive battery post which sits under the plastic gang that has the hot leads going to the fuse boxes - correct? I pulled that off and did a test which still showed 5.0A draw. You think I need to get under the truck and yank it out
There are two wires between the alternator and the positive post on the battery - A thick one (the "B Terminal") that carries charging current to the battery, and a thin one (the "S Terminal") that senses voltage at the battery (which the voltage regulator inside the alternator uses to determine how much charging current to supply).

Usually, the thick one is the one that causes significant battery drain when something inside the alternator fails.

For measuring parasitic current drain without breaking a connection, a clamp-on DC meter works well - It senses the amount of current flowing through a wire, without actually making any electrical connection to the wire. I use a Uni-T UT210E Clamp-on AC/DC Meter - It'll measure up to 100 DC amps, but also has a low range that's sensitive enough to measure just a few mA of current - very handy for tracking down small parasitic loads.
 

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Discussion Starter · #5 ·
I removed the alternator and did a diode test on the bench. It tested fine so I took it to Advance Auto and they checked it out on their alternator testing machine. They came back that it was checking out good as well.

I also unplugged the starter. Drain was still there.

I ordered a tool similar to the one Skibane linked to arrive tomorrow night to make sure the draw remains after the vehicle "goes to sleep" after I connect the battery. I may just have a bad 20 month old battery and assumed the 5 amp reading I'm seeing is the cause. Perhaps I missed a fuse and this may yet just be normal operation of the vehicle. MTF.
 

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I had a similar issue with a mazda i owned where the battery would die after a few days of sitting. i had a metra stereo dash kit installed that replaced some of the HVAC buttons etc as well as the stereo. metra tech support said my particular car was "looking for the factory radio and causing current draw" and that i needed to plug the factory radio back in, let it sit a while, then could remove it and put the aftermarket JVC back in, without unhooking the battery. i sold the car shortly after that so i never did actually try it. so my first advice is to meter the stereo power, or just put the factory one back in and see if the issue goes away... doesn't make much sense to me, escpecially on the fronty since the stereo replacement doesn't mess with anything else, but since it is something that you changed I'd start with that for kicks.
 

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Discussion Starter · #7 ·
Resolved.

I put a new battery in and the drain disappeared. The vehicle has about a 2.5A draw after the vehicle is turned off for about 30-60 seconds. After that it returns to about 0.35A.

Only thing I can think of is that there was an internal issue in the battery that was causing a drain through the system, but that should have made the battery at least warm to the touch. I was wearing gloves when I yanked it, maybe I couldn't notice it.

I'll have to run the truck through an automatic wash a few times - just to make sure all the gremlins are gone.
 
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