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Discussion Starter · #1 · (Edited)
Hello,

I have an intermittent battery drain that is starting to drive me insane and I'm looking for some fresh eyes and opinions.

My truck is a 2008 Superduty with a Cummins 12 valve/NV4500 manual transmission swapped into it. I swapped the engines in the summer and have put about 2500 kms on it. It drives good, no issues other then the horn does not work.

The truck seemed to have an intermittent draw, if it sat for a couple days it would be completely dead. But I did have it go dead a couple times over just one night.

So what to do? Hook up an ammeter inline at the battery ground and find the draw. I did this 5 times before and after waiting for ECM, VCM, PCM, SJB, BCM etc etc etc (which ever terms we would like to use) the current was 0.01 amps. All is good right? No I still found it would drain over a couple of days.

So, now the truck is parked out a friends house and I work on it when I have time. I hooked up the meter again today and "caught" it in the act. When the ammeter is hooked up this is what it reads:

5 Amps: Computers "wake up", interior lights are on then dim after a couple seconds.
3 Amps: Stuff starting to go to sleep.
1.8 Amps: More stuff sleeping.
0.5 Amps: Almost there!
0.24 Amps: It hits this then goes right back to the 1.8 amps and cycles down.
0.01 Amps: Sometimes it gets to this stage and will be completely asleep for 1-30 minutes then just wake up randomly.

So something is telling a computer to wake up, I got in the truck to listen and see if I could hear a relay click or something and narrow it down. When the meter jumps up to 2 Amps, you can hear an extremely faint "thump thump" from the speakers/the dash needles "jitter" once, I can't really explain the sound unless you've tried starting your Superduty with dead batteries. No lights come on, no other noises that I can hear.

What would cause the Smart Junction Box to wake up intermittently? Hopefully my description makes sense, I figure the more info the better.

Thanks!
 

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...the current was 0.01 amps. ...I still found it would drain over a couple of days.
There are a few possible explanations for that:
1) you're mistaken about the parasitic draw (not likely since you seem to have gotten realistic measurements);
2) the draw increases substantially (possible, since you seem to have observed it happening);
3) the batteries are ruined (post everything you know about them);
4) the alternator is not fully charging the batteries; What are the voltages across the battery POSTS (NOT the clamps around the posts) with the engine off, idling, & at high idle?

Find someone with a MidTronics HF tester similar to this: (click it & read the caption)

When the ammeter is hooked up this is what it reads:
That would be a lot more useful if you had included the elapsed time for each event.
What would cause the Smart Junction Box to wake up intermittently?
I assume there are MANY things that could do it in a stock truck. But since yours probably has a lot of conversion wiring, the list is potentially even longer.

And you seem to be assuming that the problem originates in the SJB - do you have some specific information you didn't post that justifies that assumption?
Hopefully my description makes sense, I figure the more info the better.
More details about the truck could help. Click this & read the caption:

 

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Discussion Starter · #3 ·
Hey, thanks for the reply.

It is possible I am mistaken about the parasitic draw, but my dead batteries tell me otherwise.

Battery Info:

The batteries in the truck are Nation Wide 850 CCA. There are two of them. They were bought new in the spring of this year when I started this project. Back then they started the truck great(it was still stock and had the 6.4 Powerstroke and 5R110 transmission). It could sit for a couple weeks and start no problem at -25 degrees C.

Since the drain issues started (after swapping in the Cummins engine and 5 speed) I have tested them twice with the old school "toaster" tester and they passed. After continually finding no draws I had them tested at the battery warehouse once with a digital tester (Not sure if it was a MidTronics HF Tester but it looked similar), still passed. Both of these tests were performed after driving for a long period of time (batteries were fully charged).

I have also charged them up with a battery tender and let them sit on the bench alone (hooked to nothing once charged) to check if they were internally shorted/draining down over time on their own and they stay at 12.4 for weeks.

Alternator Info:

The alternator is the stock one found on the Dodge engine. It is wired with an external voltage regulator to control the charging. One of the control wires is tee'd into keyswitch power which is shut off with a relay when the keyswitch is off to prevent battery drain. (All of the results I show already have all of this unplugged, so it isn't a possible drain). The alternator puts out 14.5 volts @ both battery posts all day long. When you first start the truck I can measure the current with an amp clamp at about 70 amps then after driving for a while and the batteries charge up it goes to about 20 amps. Its been awhile since I tested this, but if I remember right with all lights, four way flashers, heater fan, radio etc on it went to 40 amps. I can't think of any other electrical loads to put on it (AC isn't hooked up and neither is the intake air heater grid), but it seems to be working good. I cleaned all my battery posts/clamps and followed the ground wires to the frame and buffed and cleaned them.

Why do I think it is the Smart Junction Box?

Now that I have the truck intermittently drawing power I have slowly eliminated things. When looking at the truck engine bay on the drivers side: the starter power wire was removed (my starter is on the drivers side of the engine), under hood fuse block power wire was removed, this left just the battery on the drivers side which was disconnected. So it is just the passenger side battery left which feeds the smart junction box and is connected to the alternator (alternator power wire is still hooked up, it is not warm, and I figure if its shorted it would be doing it all the time and have a higher draw. I have also spun the alternator thinking maybe it has a bad spot, nothing found).

Also the fact that the power comes on and off seems to be a result of the junction box controlling something (radio speakers turning on and off and dash jitter), but thats just my opinion.

Conversion Info:

-The truck isn't by me right now so I can't read the door sticker like you described, Ill snap a picture the next time I am out there. But the truck is a crew cab short box white work truck. Pretty plain, no crazy options. Manual seats, power windows and door locks, I think this makes it and XLT?
-6.4 Engine wiring harness is still intact in the engine bay with only the crank speed, cam speed, engine coolant temp, intake manifold pressure sensor(boost) sensors attached. Only the coolant temp and boost sensor are being used, haven't found time to get the speed sensors mounted to get my tach to work.
-Since the engine ECM doesn't see RPM, it will not turn the HFCM fuel pump on, so there is a power wire run to that with a switch(has been removed and parasitic current draw still does its thing).
-Entire transmission electrical connector has been unplugged(because the 5R110 is now gone). This has made the issue of the truck will not start with the ignition switch because it does not know it is in park. Another wire with a switch to the stater solves this the starting issue for now. This is a big ??? for me, since the truck doesn't know its in park will this cause me the issues I'm seeing??? But I also think if the ECM was not seeing a park signal and it needed it, the system would never shut off.
-DPF is removed.
-Alternator wired in like described above.

As far as times for the current to settle down, it takes about 5 minutes to shut off completely when it is happy.

I took a video and I will see if I can post it later, but for now:
Truck sits at 1.78 amps then falls to 0.28 amps for 5 seconds
then falls from 0.28 amps to 0.01 amps for 1 second
then jumps from 0.01 amps to 1.78 and sits there for about 10 seconds.
And the cycle continues. Intermittently... like I said sometimes it will go to 0.01 and stay there for 5-10 minutes, then with nobody touching anything or moving anything the cycle will start up to 1.78 amps.

Let me know what you think or if I missed something. Like I said looking for some new thoughts and opinions, the girlfriend isn't to excited to talk about F350 wiring at the dinner table, haha.
 

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...I have tested them twice with the old school "toaster" tester...
That's extremely BAD for the batteries, and inconclusive, which is why Ford neither recommends nor accepts that type of test.
Both of these tests were performed after driving for a long period of time (batteries were fully charged).
If you didn't measure their voltages at rest & under a measured load (but not as heavy as the toaster) or with the HF tester or with a hydrometer, then you can't be sure they're fully-charged. I like to use an old headlight bulb because I know it's almost exactly 5A.
...they stay at 12.4 for weeks.
That's slightly lower than I'd expect, but not by much. After sitting for weeks, would they start the truck withOUT additional charging? If so, then it's a good test and they were good at that time.
...if I remember right with all lights, four way flashers, heater fan, radio etc on it went to 40 amps.
That's substantially lower than I'd expect. The heater blower alone pulls over 20A on HI. That makes me wonder about your clamp meter. Have you ever attempted to test or calibrate it? If you can measure the resistance of the toaster, then you can put a digital voltmeter on it and read the clamp current. The calculated current (A=V/ohms) should be the same as the clamp meter shows.
I cleaned all my battery posts/clamps and followed the ground wires to the frame and buffed and cleaned them.
Congratulations - you're among the rare few who understands the importance of that simple maintenance procedure. I'm always amazed when professionals argue with me about that; and they're always amazed when I show them how it fixes so many weird symptoms.
...alternator power wire is still hooked up, it is not warm, and I figure if its shorted it would be doing it all the time and have a higher draw.
That's a bunch of erroneous assumptions. The wire's temperature depends on the draw; if the alternator is only pulling 1.78A, it won't perceptibly heat that big wire. All the heat will be inside the (heavy) alternator, which will exhibit even-less temperature rise than the wire would.
I have also spun the alternator thinking maybe it has a bad spot, nothing found).
Again: that's not a test. You'd have to measure continuity between the armature & stator cores.
Also the fact that the power comes on and off seems to be a result of the junction box controlling something (radio speakers turning on and off and dash jitter)...
That's a big assumption, even though it might be reasonable. So the next step is to TEST the assumption - unplug the SJB while the draw is high, and observe the reading.
...since the truck doesn't know its in park will this cause me the issues I'm seeing?
No.
Intermittently... like I said sometimes it will go to 0.01 and stay there for 5-10 minutes, then with nobody touching anything or moving anything the cycle will start up to 1.78 amps.
That's good data, but nothing can be deduced directly from it. You have to continue testing things. I'd disconnect the batteries from each other (but NOT from the truck); then find out what each one's parasitic draw is. I assume one will be in-spec, and can be ignored. Begin near the problem battery's (+) post, measuring the draw, and disconnect it from the truck - the draw should go to 0. If not, move closer to the (+) post and disconnect until you get 0. Then reconnect & work SLOWLY away from (+) through the truck's power wiring toward the (-) post disconnecting ONE circuit branch at a time until you get 0 again (meaning you disconnected the draw). Each time the draw remains the same, reconnect & work through the wiring that you DIDN'T disconnect. Each time you get 0, reconnect and work through the wiring that you DID disconnect. Eventually, that will bring you to the draw.

Yes, it will be slow & arduous, but with a custom-wired vehicle, there are no shortcuts except the ones YOU (the person who custom-wired it) know about.
 

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Discussion Starter · #5 ·
Yes the batteries started the truck after sitting on the bench for a couple of weeks @ 12.4 volts no problem.

I said they were tested after a long drive just as a side note. The times with the toaster, no I did not test the voltage reading(or can't remember) but after testing(and them passing) I hooked them back up and started the truck and drove away.

The time the batteries were tested with the digital tester, it was a tech at the battery place he was running the machine and I cannot remember the exact voltages but we were both confident in the readings being good.

Both of these seem irrelevant to me because all test results say the batteries are good.

You say it extremely bad for the batteries to use the toaster tester. Possibly, but this is what I have access to and I believe it is a real world test of what these things go through when starting a vehicle. I don't think the test results can be dismissed because it isn't the make and model of battery tester you want me to use.

Yes my amps may seem low. Remember this is now a mechanical injected diesel engine in the truck, the only thing it needs to run is the fuel solenoid activated, which is minimal. Lights, heater fan, HFCM fuel pump, and fuel shut off solenoid thats all I can turn on.

Have I ever calibrated my amp meter, no it is an almost brand new Fluke. I trust it.

Me talking about my alternator is also a side note. You say the alternator will never get warm, that is an assumption. Google parasitic drain on vehicles and in every forum you well read one guy telling a story about how their alternator was warm to the touch, they changed it, it cured their problem. And I thank these people because it gave me something to check, I checked it, I am letting everybody know so we can skip that step.

You asked me for time intervals, I informed you, now you say nothing can be deduced from it. Thats what I figured, but..... you asked, so I will give you as much information as I know.

My "custom wired" truck is now at a state where there is only one battery left in it connected to the junction box and alternator and has an intermittent draw. All other "modifications" have been removed (except the fact that the truck doesn't know it is in park, but you seem to be 100% confident that this will not cause issues). I will go pull more fuses when I have time.

Thanks.
 

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For what it is worth - I had a Dodge one time that had a parasite. Finally caught it one day - went to pulling fuses - ended up the radio would just start drawing at any time. New radio problem solved.
 

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After reading thru all this, I was going to suggest to take the radio/speakers out of the equation and see what happens...but draymorris beat me to it.
 

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Do you have a security system on it? Some of those with motion sensors can start arming themselves when the wind blows...
 
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