There is something called a "junction box battery feed" , fuse #22 under the hood. When I pull that it drops. Nothing else. But doesn't that keep everything from working or isolate the batteries????? I don't know where it is or what it does.

I found a test light. It lights up pretty bright. Are there any inline fuses?

Not sure if this has any bearing or not, but there is a vacumm leak. Not sure where. It has to do with the vents for ac and heat etc.

 

Bob, this is from another site: Check the engine harness where it crosses the valve cover on the drivers side. If it rub through the wires there it will blow that fuse.


as for the vacuum leak, check the little hose that goes from the vacuum tree to under the heater box. that is the one that supplies in cab vacuum for heat/ac controls. it tends to break rite near the heater box in the engine bay.
if not there, then check passenger foot well up under the dash under the carpet. there is a vacuum splitter there that sometimes will pop a line out if stepped on too many times.

 

problem with test lights is they are not all equal and use different current rated bulbs and they cannot give you a true indication of the draw... while I don't dispute that they are handy tools

 

The testlights work pretty good, and looks like it worked in this instance also.

With these modern vehicles with battery saver circuits in them, you have to take the key out and shut the door. There is a guy on here that works on these things and claims you have to wait up to 40 minutes before you can check the draw. On my truck at work, it seems like most it shuts down after 10 minutes, but you can wait 40 minutes to be sure. Double check if there are any non factory wires coming off the battery. They need to be pulled too and then the draw checked. If nothing brings the draw down, pull the wires off the alternator. If that works, then you might have a bad diode in the alternator causing it. It happens once in awhile. You should not be over .07 amps. Like someone said, .03 is more like it.

 

which is exactly what I was referring to in post #30


The point is that a Bulb is a Resistor and will be limiting current to Modules and this can cause the Modules to behave badly (as in not wanting to go to sleep for 1)
where as the Ammeter is Shunt based and does not Limit Current like a Light Bulb.

EDIT By Franklin: Good theory, but in actual practice they still work. I am not against using a meter, you always need to take the high road if you can. But some guys on here do no realize not everyone is a electrical or electronic technician, even the guy above had some trouble getting his meter setup properly, getting it working correctly, and then needing help interpreting the numbers. As long as you get the testlight in the circuit correctly, it needs no configuration or setup, and to interpret it is easy. It's either lights up bright or does not light up.END EDIT


My EDIT: while I don't mind the EDIT and I partially Agree with your point, it's no reason to not Teach Proper procedures especially on these newer vehicles that are packed full of electronics.
A meter is Mandatory for electrical troubleshooting... the Theory I posted is Correct Current is common in a Series Circuit and only Voltage is Common in a Parallel circuit.


We are here to help folks so if one does not know how to do something then we Help them to do that....

 

I was able to check for codes. The following came up:
GEM
B1352 ignition key in circuit fault
B1318 battery low voltage - THey are about 11.65 now.
B1302 Accessory delay relay circuit failure

Overhead trip computer
P0500 vehicle speed sensor A
B1203 fuel sender circuit failure

Enhanced Powertrain
PO603 internal keep alive memory (KAM) error
P1106 Dual alternator lower fault. - this might be there because I started it the first time with only one alternator and no belt. Both were just rebuilt.

Can any of these cause a short?

 

OK still too high ... 0.33 A = 330 mA ... so what else is common on that fuse.. it may be that pulling that fuse is just part of the equation.
See my last post again.. I did an Edit and added more information that you might find helpful.

 

when I put everything back together and found out it wouldn’t start, I decided to pull the negative cables off to limit how much the batteries would lose. Does this mean things are shut down? Or do I need to hook up the batteries for an hour or so and then disconnect again?

 

I think I confused you, I confuse myself sometimes. Of course you will not get a draw on the batteries with them disconnected. What you need to do is connect them up, while also setting up your testing apparatus and hooking it inline, leave the hood open, make sure there are no hood trouble lights connected, turn the key to off, shut the door and walk away for 40 minutes. When you initially do this, your amp draw will be normally high. After 40 minutes you can come back, the truck should be fully "asleep" and then you can take a peek at your amp draw.

I haven't experimented with these late rmodels to know, possibly opening the door may "wake it up" again and once you do any experiments with pulling fuses, you may have to walk away again for 40 minutes. Of course having the door open is going to turn the domelight on so that little draw there will ruin your troubleshooting.

I think if you came back after your first 40 minute thing to put it to sleep, and your draw is still .x and not .ox, then I would start messing around under the hood without opening the door. You could pull the wires off the alternator, and you could also pull underhood fuses. The underhood fuses would kill large sections of the truck and you could narrow it down that way. But I am curious about the alternators myself. When you test them make sure you take the small wires off and the fat wire or wires too.

 

So I did all that but still had the same draw. I will try the alternators next. Is there a place to get a wiring diagram for this truck? There isn't much in the Haynes manual.

 

Tom is this the thing under the dash you were talking about? It looks like there is something missing from it. I will check the harness on the valve cover too.

 

The only place I know of right now that might have a diagram is a app in the google play store called Carmin.

 

yup, that is it Bob. with engine running hold your finger over the open nipple and see if there is vacuum to it.
the big problem is going to be finding the missing line.

 

Well I pulled things apart. I took every fuse and relay out of the box under the hood.Nothing changes until I pull #22. Battery Junction Box. Does anybody know what that is or where it is? With all the fuses out, the smaller panel in the cab is dead. I disconnected the plug over the valve cover. It didn't change anything. And I inspected the wires. So the battery junction box is the culprit. Whatever that is.

 

Fuse #22 feeds the Central Junction Box ..Lower LH side of Dash ...

That Feeds fuse 13, 15, 1, 12, 3, 4, and fuse 14 <<=== pulling those fuses is the same as pulling Fuse 22 in the engine compartment fuse box.