I am having an issue with my battery draining when my truck is off. I tried to troubleshoot it today by pulling the negative battery lead and putting a multimeter on the positive lead and the block. I pulled every fuse and the draw did not go away. My grounds look solid too. The draw is weird it starts off at around 300 mV and then slowly decreases down to 10 mV and then stays there, very strange.

Any ideas where to go from here?

 

Sounds like you're feeding an RC circuit; the cap charge current starts off high, then tapers off.

You don't have an aftermarket audio amp, do you?

 

Nope everything is stock.

 

Any other ideas where the draw could be coming from?

 

How old and in what shape is the battery ?, also can you test the alternator to make sure it's charging enough......and I recall some talk here of a diode self destructing in the alternator which would let battery voltage drain back from the battery

 

Brand new battery. I pulled the alternator fuse and the draw did not go away, I will try to disconnect it and see.

 

have you tried pulling relays or fuses to isolate the issue? like radio , abs, etc

 

Yes like I said in the original post I pulled all fuses and relays one at a time, nothing.

 

everything that is connected to the battery (that could draw power) should be connected through either a fuse or a fusible link. If you pulled every fuse and the battery still lost its juice, then I would say it is a bad battery, and just because it is new does not mean it is good.

but here is a question, you said the drain is about 10mV, did you mean 10mA? if so that is probably a normal parasitic key off draw. Now if your problem is the truck has trouble starting I would test the alternator because it sounds like the battery is not being fully charged.

get me a couple readings with your meter, check battery voltage with key off, and battery voltage with truck running. and be specific let me know exactly what the meter says (if it fluctuates over about 5-10 seconds let me know the range it fluctuated)

 

Yes sorry mA. But I am thinking I did not measure it correctly. To get in series I should have pulled the negative battery lead then put the multimeter on the negative post and the block. That would put it in series correct? Maybe it is just normal parasitic draw and my battery is dying.

I'm pretty sure it is my battery though because when I come home from a long drive and put it on a charger it is charged up. It is only when it sits in the cold for a day or 2 that I have issues.