Parasitic Battery Loss Tracing
 

Hello all, I have a 2007 GMC Sierra 1500 Classic that I am trying to run down a battery drain that is driving me crazy. I think it is the drivers door latch switch but I want to be sure. I disconnected the battery negative terminal and put my meter in series with the negative side of the circuit and tried reading what the draw was. On the initial connection the meter reads 2.5 amps, multimeter set on 10amps and plugged into the 10amp port, but after about 5 or 6 seconds the amp reading drops down to zero and doesn't go back up. I left the meter connected for at least ten minutes and got nothing. I thought I may have popped the fuse but I checked the fuse and that was still okay. Am I missing something or overlooking something? Is it because the 10amp port is fused? Everyone else I see testing the circuit has an unfused meter so I'm not sure. Automotive electrical is definitely not my strong suit.

Also for reference the battery has been left disconnected on the negative side for 24 hours and the voltage is reading 12.42 VDC. Made sure to switch the ports going from amps to volts and back to amps.

Any suggestions or something I am doing wrong? I am pretty stumped. I would think I should just be getting a constant reading the whole time the leads are connected.

Yes, that is the correct procedure for checking amperage draw at the battery...

On my GMT800 suburban that had a instrument cluster parasitic drain, I remember when I got it fixed, there was something like a 15 mA draw, so you should be seeing something around that. Confirm your meter is working, maybe try another vehicle. Just don't try cranking because that's when you'll blow the 10 A fuse.

You can also do a voltage drop test at the fuses. Simply test the voltage across the fuse contacts. There's tables that will have amperage listed based on how much voltage you are reading for the different fuse amp ratings.

If you had an infrared camera and live in the cooler regions, you can also try looking around to see what circuit, actuator or whatever shows up as "hot." Obviously on a completely cold engine.

I hope this helps.

So just an update for anyone reading to see if you might have something for me to check.Alright got a new meter and tested things tonight. Still getting 2.5 to 2.7amps on a test with the negative terminal disconnected and meter connected on the lead and the battery terminal.

My question now is to get an amp reading I have to move the meter around but not the negative cable. I was thinking maybe a bad ground but I am not moving the cable so I am not sure what might be going on. I do believe in the sporadic readings that my issue has been isolated to LBEC 2, but I just ran out of light tonight to keep testing and not getting a continuous reading was getting irritating testing alone.

Any ideas on the non consistent reading?

Here's a pretty simple video showing the basic test procedure:


One thing to keep in mind when using this method of pulling fuses, when you put the fuse back in it could wake up the module causing your reading to spike up and you'd have to wait for it to go back to sleep. So, it's probably quicker/easier to pull one fuse, check the meter, if no change, pull the next fuse and so on until you get the right one.

If you have the hood up, go ahead and disconnect the under hood light while testing.

An auto ranging meter makes life easier, but they do cost more.
IMO you don't know about ohms law to really troubleshoot with a amp meter.

I use one of these for checking results at the cables.


https://cimg2.ibsrv.net/gimg/www.per...b87a7513de.jpg

It's not a "bad ground".

2½ amps is A SHIPLOAD of current. Sounds more like a light is left on somewhere.

That makes no sense whatsoever. I can't understand what you're saying.

Use alligator clip leads, https://www.autozone.com/miscellaneo...706/297077_0_0 for example. Clip the black meter lead to the batt neg terminal (you can put a short bolt in the terminal to clip onto), and the red meter lead to the neg batt cable. Make sure nothing is touching anything else metal. Put the meter on Amps. Take it out of Autorange if it has such a switch. That'll keep it from switching ranges whenever you make a change. Post a pic of your meter and maybe we can tell you what to do. Set it to the 10 amp range to begin with. Not saying this will "cure" "sporadic readings", butt if you're not accustomed to using a DMM, it helps for the meter to stay doing the same thing at all times, and not jump around as the quantity it's trying to measure takes big steps.

LBEC2 under the hood is a sort of "master" fuse, that feeds a whole bunch of further fuses in the sub fuse block at the left end of the dash, right behind the door. If you hook the meter up as described, and LBEC2 drops the current from 2.5 amps or whatever to something very near zero, then some one of the circuits fed from that sub fuse block is at fault. The fuses in question are probably the DDM and PDM (door modules), Aux Pwr, ECC (HVAC), and Locks. Plug LBEC2 back in and repeat the test by unplugging each of those.