Something "wakes up" and draws current in the night.

[Dirtman]

I've been fighting an electrical gremlin for months now. Every couple of weeks my battery will be dead in the morning. I charge it back up and it works perfectly fine for a while then does it again.

Truck is an 09 2.3 auto base model. Battery is 2 years old and holds 12.65 volts after a charge. I put it on a load tester and it tests perfectly fine. So I moved onto parasitic draw tests. This is where it gets weird.

Initial draw before the computer sleeps is 197.5 mA. After 5 minutes it drops to 71.1mA (computer goes to sleep). After another ten minutes it drops to 8.6 mA (something else goes to sleep). So those numbers are good... BUT, leave it for another 30 or so minutes and the draw jumps to 134.2 mA. Something is "waking up". I pulled every single fuse in both the power distribution box and the smart junction box but once that 134.2 mA draw pops up nothing kills it. If you wake the computer up by opening a door or whatever the same thing repeats. Starts at 197.5 mA, then 71.1 mA, then 8.6 mA, then the mystery device wakes up 30 minutes later and draws constant 134.2 mA. Rinse and repeat.

Any ideas? Heak is 134mA even enough to be killing my battery? I drive the truck every day except weekends. (Usually the no starts happen on mondays so sitting 2 days max) The alternator puts out 14.6 at startup and drops to around 13.6 after 10 minutes of driving so that looks good as well.

 

[adsm08]

134 mA is enough to kill the battery in about 36 hours. Rangers have stupid small batteries too.

Ford says max should be 50 mA, so you are almost three times the spec there. Next time you do the test pull the relays too. I have seen at least one instance of a relay causing a parasitic draw that did not show at any of the fuses. On the one I can remember it was the wiper relay, problem only showed up after it rained, took me three visits to find it because nobody knew that detail, it just happened to be raining the day they brought it in for the third time.

 

[Bird76Mojo]

I had the same problem on my 01 4.0 and solved it by fiddling around under the drivers side of the dash. There was a bank of relays under there. I could feel one relay that was warm all the time. I pulled it, installed another one out of a parts truck, but I still had the same parasitic loss. So I re-installed the original and the problem went away.

But I also installed another GEM module from my parts trucks during the process. Classic mistake of swapping too many parts at once. lol


GB

 

[Dirtman]

I just "woke it up" throwing my tools back in the cab so now I gotta wait for it to go back through the sleep phases before I can pull the relays to test if it's one of them. There all in the power distribution box on my truck. I don't have a GEM and I have no power options so there's none on the SJB.

 

[RonD]

Door switch maybe

 

[adsm08]

I just "woke it up" throwing my tools back in the cab so now I gotta wait for it to go back through the sleep phases before I can pull the relays to test if it's one of them. There all in the power distribution box on my truck. I don't have a GEM and I have no power options so there's none on the SJB.

When it spikes back to 134 wait about 2 or 3 minutes, and then just feel them. That should be enough time for them to get hot. If you get a hot one pull it first.

 

[8thTon]

Do you hear any clicking under the dash? My 2004 had a defective turn signal/hazard switch that put just enough load on the flasher relay to cause it to operate randomly, whether the truck was on or not. No lights flashed because the switch positions were not set to connect them. I've read of another 2004 with the same issue, so perhaps it affected others. I replaced the switch with one from the junkyard which fixed it.

 

[Dirtman]

Ok before I went to bed last night it was still at 8mA, never spiked back to 134mA. The issue is if you disconnect the negative battery terminal the computers wake up the second you re-attach the negative cable or the DMM leads. So I have to run a jumper wire from the ground post to the ground cable, then attach the DMM leads, then disconnect the jumper to allow full current through the DMM without disturbing the computer. God I hate technology.

I did just that this morning before leaving for work (had the jumper wire on all night) but for some reason as soon as I attached the DMM, even with the jumper wire still on it made enough contact or whatever to wake up that damn 134mA draw. If you sneeze near this thing the computers wake up...

Anyway with the 134mA draw happening I felt and pulled all the relays. Again nothing killed it.

I did the math 197mA initially, then drop to 71ma, then drop to 8ma.

197 - 71 + 8 = 134. So... the 134mA draw is the same as system that initally shuts down after 1-2 minutes dropping from 197 to 71 mA. Whatever that system is, is what's randomly "waking up".

I hope that made sense and my logic is correct. If it is... WTF IS THAT SYSTEM? And more importantly what causes it to turn on by itself? My shop manual says the Airbag/SRS system stays active for aprox 1 minute after shutdown so that adds up time wise. And the issue started aprox 6 months ago when ford did my airbag recall. Dunno if that is related but its all I have to go on right now, however I remeber pulling the airbag fuse and it didn't kill the draw... im gonna start over pulling all the fuses and relays again after work.

 

[Dirtman]

Ok update. I misread the shop manual. The ABS system has a capacitor that can hold a charge for 60 seconds after shutdown. It doesn't draw power after shutdown. So that theory is dead. The past two days it hasn't been happening. It comes and goes like a fart in the wind. Im half tempted to just install one of those priority start battery protector relays that disconnect the battery if the voltage drops below 12 volts... at least it will give me some peace of mind until i track down the issue.

 

[8thTon]

Nocturnal current emissions?

 

[snoranger]

We had a random parasitic loss issue on a truck at work, it sat in our other shop for 9 months until they sent it up for us to look at. 5 minutes later we found the issue.

Bad alternator. It would come and go depending on where the alt stopped spinning. I pulled the belt and turned the alt slowly. The current draw only showed up in certain positions.

 

[Dirtman]

Well, thats at least a new direction to look at. Thanks. I'll add that to my list of tests after it stoos raining.

 

[RonD]

I doubt drain would stop and then come back if alternator was at fault

2009 uses Smart Junction Box(SJB) as the Body Computer, 2004-2011, GEM was used in 1995 to 2003

SJB controls all the body electrics

I have wiring for 2008 SJB, attached below
In 2008 it looks like fuses 1, 3, 5 in Engine fuse box supply full time power to SJB

Key on power is not an issue, nothing powered by key on can "wake up" on its own

Also added the power distribution for 2008, sorry I don't have 2009, but they will be the same except for fuse numbers

Fuse 1 powers specific devices, as does Fuse 3 and Fuse 5(in 2008)
So if you pull one of these fuses, and amps drop that will narrow down, "whats on", at that moment

And you could pull all 3 fuses, over night, or ?? and if battery wasn't drain again then SJB circuit IS where problem lies
If battery drains then it's a device that is battery direct, wiper motor, ABS module, computer, or EVAP Vent

 

[Dirtman]

Thanks for the info ron. I just bought a fuse adapter test lead for my DMM so I can do current draw right on each fuse circuit individually instead of hooking it to the battery then running around after pulling each fuse to see if the current dropped.

Ill start with fuse 1,3,5.

The problem with pulling the fuses and seeing if theres no drain overnight... It doesn't happen every night. It's random which is why this is such a pain to track down. I can go 2-3 weeks, sometimes even not starting the truck for days and not loose a hundreth of a volt on the battery, then one random morning its drained down to 11 volts.

 

[Dirtman]

Ok heres my findings....
At the power distribution box under the hood these are the fuses with current draw with everything OFF.

Fuse #1 is 1.82 mA, insignificant draw
Fuse #3 is 132.4 mA, (interior fuse panel SJB)
fuse #21 is 0.78 mA. insignificant draw

On the interior fuse panel SJB the following fuses have current -

Fuse #11 66.5 mA (smart junction box logic power)
Fuse #24 1.78 mA insignificant draw
Fuse #33 132.4 mA (instrument cluster battery feed b+)

So fuse #11 and #33 are my issues. Fuse #11 goes to sleep but doesn't seem to wake back up but #33 does. #33 will go to sleep after a minute but it is woken back up by pretty much anything (opening the door, hitting any of the lights or and switches ect)

what is instrument cluster battery feed b+ and any ideas why it wakes up randomly in the night?