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Diagnosing Parasitic Draw

20K views 33 replies 15 participants last post by  timkarp 
#1 ·
So my X has been out of commission for a while now. I only drive it a couple times per week and I dunno if it's the cool weather or what, but if I don't drive it within 3 days it dies on me.

I've got a trickle charger that I use to top it up, but I've been trying to figure out what could be causing this. I've had the battery tested in 3 places and they all say it's awesome (Diehard Platinum).

The alternator 'barely' passes.

So I've been thinking the alternator isn't fully charging the battery, but I decided to do a parasitic draw test.

I followed the instructions from this video, which is really well done:
http://www.youtube.com/watch?v=KF1gijj03_0

I do exactly as he does - set my multimeter for 10 Amps, disconnect negative battery cable and clamp the multimeter leads to the negative terminal and the negative battery cable.

When I first do this there's a slight 'surge' in activity that measures around "0.80" on the multimeter. I figure this is when the dash flickers, the ECM is booting back up, whatever.

After a few seconds everything settles down and the amps sit at around "0.15" plus or minus 1.

So that to me seems like a relatively low draw. I pulled a bunch of fuses and nothing affected the multimeter.

So - Is theory number 1 correct? Alternator isn't charging the battery enough and so it just drains down and dies after driving the X for awhile?

Or am I performing the parasitic draw test wrong? I thought for sure it would be my offroad lights or something, but I have all of those accessories going through relay's and switches - and when I pull their fuses, nothing happens.

Thoughts?
 
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#2 ·
0.15 amps is less than 2 watts worth of power. Nothing. The truck ought to be good for a few weeks at that if the battery is good.

You can take the battery to PepBoys and they'll test it for free.

Start the truck up and measure the voltage across the battery terminals - it should read 13.6 volts.

Shut the truck off and it shouldn't drop below 12.6 volts.

Do the lights dim when you let the truck idle? Does the dash lights dim when you turn the headlights on? - these are indicators of the alternator struggling to keep up. If the alternator is bad the truck will not get enough current even while running.

The Xterra is kind of high tech in that there's a module on the negative lead that measures the current draw and adjusts the output of the alternator to match. This is done in the name of energy efficiency likely saving 0.05 miles per gallon. If there's a problem with that module or the circuit behind it the alternator might not be charging the battery.
 
#3 ·
Thanks Paul - I did as you advised, and the voltage works out exactly.

So, now I'm at a loss! I have two sets of off road lights, I'm wondering if maybe there's an issue with them since I tried turning them on, and all of a sudden they don't work. Fuses are good, which is making me think the relay's are bad - even though I can hear them 'click' off and on along with the switch. Ugh.

I'm going to keep digging. I managed to get a cheap Coleman solar battery maintainer I'm going to keep in the X for the time being and see if that helps at all, but that's clearly a band-aid at best.
 
#4 ·
You know you have a draw. You know it kills the battery. Forget the amount for a second.

Hook up your meter and start pulling fuses one at a time until the draw stops. Then you'll know which circuit is shorting. You'll really narrow down the problem. If you can leave that circuit interrupted, or disconnect when you park for the night, you can learn whether the problem goes away.

Then focus on that circuit testing wires for a short to ground.
 
#8 ·
Done that. Battery still died after a few days :(

I's super frustrating. Battery testings says it's good, alternator testing says "technically good but not great". Current draw is very low. A couple random accessories don't seem to be working. Makes me want to rip the thing apart.

Surf, with your inverter - is your negative cable attached to the battery post? I'm wondering if it's something to do with the chip / circuit thing that is attached to the negative terminal.
 
#9 ·
Charge it up
Unhook the battery.
Wait your magic 3 days.
Hook the battery up and see if it starts.
Yes, battery OK
No, you have a drain.

Alternators can have an internal leak and pull a battery down. But usually faster then 3 days. Try unhooking the alternator and see if that takes out the .15A draw. I believe that can be done at the battery.

Anything aftermarket? I have seen GPS tracking systems suck batteries down. Stereo amps that don't fully shut down also do it. Some aftermarket alarm systems are power pigs as well and on all the time. I don't trust any aftermarket electrical items.
 
#10 ·
Did that - Battery was OK.

Definitely have some aftermarket stuff. Pulled all the fuses on them, no change. But, a few of them have stopped working in general making me think it's their relays or something. Maybe it's a bad ground somewhere.

I'll try disconnecting the alternator when I get a chance and see if that changes anything.
 
#19 · (Edited)
Edit - NM.

Measured voltage across terminals, got 12.45, figured it wouldn't crank - it did, without skipping a beat.

Then I moved the inverter cable to the body ground. Fired up the X and it showed only 13.1 volts. Shut it down, tightened the ground bolt, and it's back up to 14.3-14.7 charging.

So - we'll see how it goes. About to take her out for a run to the landfill, then picking up a friend at the airport. Lots of driving so I'm hoping to see a charged battery by the end of it.
 
#24 ·
also, are you getting a .15A or .15ma draw? if you are getting .15A that is 150ma...WAY too high. you need to make sure the computer is sleeping and all accessories that have the ability to shut off....like an under hood light...are off before you take a draw reading.

i used to be a benz tech and we would hook an ammeter up in series with the neg battery cable, close and lock the doors, wait 10 min, and take the reading. a loaded w210 (e-class), which had way more electronic gizmos in it than an X, only pulled about 30ma at rest if i remember correctly.
 
#26 · (Edited)
hopefully someone can get you a normal draw reading soon so you will know what your reading means, but 150ma seems too high to me. i'd keep going and pull all the fuses/relays, one by one through all the loads (factory or aftermarket) until you see a change. if you do have a draw you'll find it eventually.
 
#28 ·
I read in one of the Nissan manuals somewhere that when you hook up something electrical, such as an amp or power inverter, never connect directly to the negative terminal. The charging system can not get an accurate read of the draw on the system and battery, therefore not charging the battery properly. Also, .15A sounds like your power inverter is not turning off. Mine is hooked up to a switch with a relay and i had the same problem. Issue turned out to be a bad ground for the relay. Good luck with hunting it down, electrical issues can be such fun. And did you have the ipdm recall done?
 
#31 ·
Just wondering if you had made any progress on this? Im having the same problem with a constant draw of about .095 amps, been pulling fuses and wires and tried everything. Have you come across a diagram showing what the connections are to the positive battery terminal? there are two spade connectors and two plugs running up the backside and I want to unhook those to see which one the bad circuit is on but even once I do I cant find anything saying connection is for which circuits... :scratch: :confused:
 
#33 ·
Similar issue here. Ended up buying a priotitystart device. Check out my thread in the electrical section titled "battery protector"
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