Mystery Battery Draw While Parked UPDATE

[BFL13]

Update 13 Jan--
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Never know--somebody on here might have an idea what to look for, thanks for any help.

2003 Chev 2500HD LT (so has lots of electrical stuff that works with ignition off) 6L gas.

Problem is the battery voltage goes down too fast while engine off parked overnight. Say 12.6 evening then 12.5 next morning then 12.4 next morning, etc.

In theory you can find a mystery draw by pulling fuses one at a time, but there are a kazillion fuses, so it would be helpful to know some likely suspects as nothing appears to be "on" when left overnight.

I took one cable off the battery inserted meter and confirmed there is a steady 0.74 amp draw. I don't know what is a normal amount but this seems high at 18AH a day.

I had the battery load tested and it was in excellent shape with a 400 amp draw and bounced right back. I charged it up and let it sit and it has no unusual self-discharge after a few days. So it is not the battery, it must be a mystery draw AFAIK.

I cannot relate when this started to anything that happened. Years past ISTR it would sit at about 12.5v for long periods while parked. It has been kept plugged in at home mostly with the camper on so the engine battery has been floating at 13.x volts, so I can't say when this all started. Notice it now with the camper off.

The battery dash light glows dimly with ignition off, but it has done that for 19 years. The dash shift indicator lamp is out, which is fairly new- can't see what gear you are in.

So what are some likely suspects that I could check by pulling their fuses or circuit breakers?

[patperry2766]

Had a similar problem on my 2013 F-150. If I disconnected the battery and reattached it after I turned off the truck, then everything was fine.

If I didn't then the battery would drain. Turned out that the ECM had to be replaced. It wasn't allowing the truck to shut down.

[Fisherman]

Just a stab, I don't suppose any of you have one of those electronic anti rust devices. My neighbour had a 2011 GM and it would drain batteries after 3-4 days, once he found where it was attached and connected, he threw it far, far away, it was rusted worse than a 1990's ford.

[N-Trouble]

Have been dealing with similar problem on my 2012 Duramax. Every morning I get a weak start and batteries are ~12v. It doesnt matter if the truck sits one night or multiple nights it will not continue to drain. Its like it hits a cutoff voltage of around 12v and stops draining. Have replaced batteries and just last week the alternator. Problem is still there. I have not added any accessories to my truck. Its basically bone stock.

[BFL13]

travisc wrote:
Take a look at this video on YouTube watch Wes work, he’s got a channel as a small country mechanic and fixes all kinds of things this video applies directly https://youtu.be/xEEtmdUckvI

https://www.youtube.com/watch?v=xEEtmdUckvI

Yes the parasitic draw part is close to what I was trying to do.

Lots of good ideas coming in, but I have given up now that I know I can operate with it as is. Way too complicated for little me and my multimeter!

Thanks all for trying to help.

[Grit_dog]

garyp4951 wrote:
Check the body of the alternator for voltage, or remove the hot wire to it.
I had one that was bleeding voltage from the connecter post to the body.

OP already has an issue in this area likely, so great suggestion.
Was suggested, but not responded to or even acknowledged.
But sounds like his attention span is as short as his will to fix this problem. Been more time spent on this thread trying to help him diagnose it than he’s spent trying to fix it. And apparently he’s thrown in the towel after 1 attempt.

[garyp4951]

Check the body of the alternator for voltage, or remove the hot wire to it.
I had one that was bleeding voltage from the connecter post to the body.

[BenK]

Turn off any "automatic" anything

Headlights, BlueTooth, navigation, monitir, etc

They *ALL* check in on a regular basis and some have a "power up" & wake process

[travisc]

Take a look at this video on YouTube watch Wes work, he’s got a channel as a small country mechanic and fixes all kinds of things this video applies directly https://youtu.be/xEEtmdUckvI

[BFL13]

Got started on this. Leaving hood up, can't find any ajar switch.

Tried to leave driver's door open (only door that needs to be open to get at the fuse boxes in there) and jam the open switch with a screwdriver (no luck there) and with other things still no luck. Leaving it closed for now to at least get the amps reading an hour from now.

There is a sort of spring- loaded lever above the door latch which is mounted in the end of the back half door (which is a "suicide" facing door that opens from the front end). There is also a push button in the end of the driver's door higher up. I am guessing it is the lever thing that needs "fooling" based on advice I got above, but I have not found a way to jam it yet.

I rigged up a jumper wire between the neg post and the disconnected neg terminal, and have a wire nut in the middle of that wire. I have the meter set to amps with a clamp fixed to one lead and the other lead jammed in the neg post so I can clamp the meter to the neg wire terminal as desired.

So with the jumper wire connected via wire nut, voltage is 13.2 (from just having the maintainer taken off), and amps on the meter is zero.

With the meter still connected and showing zero amps, when the jumper wire nut is taken off the amps jump to 0.20 amps. I don't know what happened to that 0.74 amps from before.

So back later with the amps reading I get after the hour long wait.

EDIT--it only dropped to 0.18 amps. Not clear I got anything done. Probably messed up the procedure somehow. Anyway, I will just leave the battery maintainer on at home and live with that.

Thanks all for the info and tips on this whole thing. Back to regular programming.

[BFL13]

I can't see any wires to the hood latch like in the above link. Can't see any push-in switches.

How does the jumper work to preserve the connection when you go to do the meter in series? If you leave the jumper there, don't some of the amps go down that wire instead all of them through the meter?

Edit: once the meter is on, you can remove the jumper?

Meanwhile, today the voltage is down to 12.35 after four days parked, dropping almost 0.1 a day. So I can leave it parked off-grid for a long weekend and a bit and it will still start.

That leaves the battery less than full for long periods and it will sulfate. If I bring it up each time it gets low at home, that would be deep-cycling the starting battery, and letting it sulfate, so the way things are I need to plug in the maintainer when the truck is not being used. I can live with that if need be.

Plan is to recharge the battery today and keep it charged. AFAIK its state of charge does not affect the mystery draw to be tested for again tomorrow.

[Krusty]

Beergardens is correct. Connect amp meter in series, or I just use a jumper wire until I am ready to watch the draw. My meter times out after several minutes and it will open the connection when it does. You do not want to break the connection. Let it sit undisturbed for an hour so the modules go to sleep. It shouldn't draw more than about .050 amp (50 milliamps) after this. You want the doors and hood open so you can disconnect fuses to isolate the draw. Just use a small screwdriver to latch the door latches fully to simulate the doors being closed.

[BFL13]

beergardens wrote:
You need to open both doors and the hood fully for diagnostic access, then disable all the door/hood ajar switches so the vehicle thinks they’re closed. Then you need to disconnect the battery and put your ammeter in series. After that is all done, you need to walk away for an hour so everything times out, keeping in mind that if you open a door or a connection, you’re going to wake everything up again and your reading will no longer be accurate.

Goodness!

It also has two back half doors, but anyway, except to open at first to pop the hood why do I have to leave the doors open and then fool them? Why not just close them?

Where is the hood's ajar switch? Edit--like this with the plug-in?
(no idea why it is in Spanish 🙂 )

https://www.amazon.com/-/es/Dorman-820-200-Conjunto-pestillo-para/dp/B01LREVJPM/ref=sr_1_3?__mk_es_U...

I can use clamps on the meter leads so I can leave it connected like that.

To save meter battery can I turn the meter off and it is still making a path in series or does it have to be left on reading amps while waiting that hour?

[beergardens]

You need to open both doors and the hood fully for diagnostic access, then disable all the door/hood ajar switches so the vehicle thinks they’re closed. Then you need to disconnect the battery and put your ammeter in series. After that is all done, you need to walk away for an hour so everything times out, keeping in mind that if you open a door or a connection, you’re going to wake everything up again and your reading will no longer be accurate.

[ktmrfs]

we had a 2004 Silverado. couple of other things to check
1) make sure ALL the interior lights are off. It's amazingly easy to accidentally turn on one of the front or rear overhead lights and not realize it.
2) IIRC not all the 12V outlets turn off with ignition so make sure you don't have anything plugged into the outlets
3) Double check that the visor lights are off. Again, another easy one to accidentally leave on.

Once the Silverado goes into full sleep mode, current draw should be in the few 10's of milliamp range IIRC. But on initial shutoff it can be 1/2 to 1 A.

Lastly, on the diesel, the battery power to the trailer plugs is ALWAYS on, even with ignition off. I don't know if that is the case on the gas or not, and it may depend if you have the one battery or two battery option on the gas engine. So if you have anything hooked to the trailer plug, I'd disconnect and see if the problem goes away.