Battery Won't Last The Night

[Nd4SpdSe]

So after getting a whole wack of work done, while the truck is at the mechanic, she developped the symdrome of draining the battery. My original battery wasn't the healthiest, so it's replaced with a loaner and is still being drained.

I went though and hooked up a multimeter inline of the positive terminal of the battery. My mechanic said the magic number is around 0.01 to 0.02 amps of draw. I'm sitting at 0.11. To me that's not alot, but it's not what it's apparently suppose to be. I went through the truck, disconnected a bunch of stuff, even the alternator, my inverter, the CarPC than went though the fuse pannel to where I pulled every single fuse out, and eventually pulled (of course, the very last one) ELEC B. My draw dropped down to 0.02. This fuse seems to control the interior lights, locks and factory alarm, but not sure what else. My aftermarket alarm doesn't add to the draw of the system armed or disarmed, so I know that one is ok, but with the fuse pulled, it doesn't lock the doors, nor go off when the doors are opened since it's triggered by the interior lights.

So I'm not sure what could be doing this, and what to test next on the ELEC B circuit to see what is the culprit? What would be most likely to be causing this?

No the interior lights are not on

[fleurys]

You did not say but I will assume everything on this ELEC B circuit is working properly ?? if not I would check these first (door lock for example or burnt light etc..) ... I<m not sure how the xterras are made but if it is possible for you to do it, I would start by disconnecting whole connectors at a time..Like the whole left door first, then the right...There must be a <master> connector for each side etc.... I don't know why but I have a feeling it's with the door lock.... I've seen this on my old gm that I had long time ago where I had a volt meter in the car and when I was unlocking my doors. Sometimes the door lock actuator would 'stuck' for a second or two. I would know it because the volt meter would take a hit as the needle would go for the low side. Then it would be ok...

Hope you find it...electric problems are a real pain...

[Bow_Tied]

Had a similar problem on my wife's Ford Probe years back, a real head scratcher. Turned out the passenger sunvisor vanity mirror light was not shutting off properly but you could never see it with the lid closed and the sunvisor up. Found it by fluke. Check the last accessory you added to make sure it is all wired properly still. Then verify EVERY light on the circuit for the mirror, maplight, glove box, rear hatch light, under dash, ashtray, etc. Failing that you will need to trace with an schematic I think. G/L

[Snafu]

Glad you tracked it down to one circuit but now you have to track it down further. Start unplugging what is the easiest...door locks, overhead light, etc. Unplug and test to see if the draw is affected.

[Nd4SpdSe]

Indeed, fortunately the weather look like it may co-operate today agani

Well, good news is with that fuse pulled, she's still alive this morning.

[keith]

in my experience its 30% glove box light 20% interior light 20% trunk light 15% brake lights 15% after market products

[Nd4SpdSe]

I've worked and isolated everything on that circuit. I got down to the control module known as the "Smart Entrance Control Unit". It has 3 connectors on it, so I've disconnected the connectors one by one, and even my aftermarket remote starter/alarm. I've even worked at disconnecting the fuses in the engine bay to isolate some of the circuits running to the SECU. The one connector where the problem can be isolated have wires running for:
- Ignition 12v (From Interior Fuse 28 - 7.5a)
- Interior Lights w/Battery Saver
- Power (From Exterior Fuse F - 40a)
- Dook Lock All
- Door Unlock Driver
- Door Unlock All
- "Headlights On" Buzzer
- Ground

The way I look at it, it's gotta be a problem with the module:
- Interior Lights Battery Saver : Even if I turn on the lights manually, they do have a system to turn them off after a while. I curse at this when I go camping. If this system isn't working like it should, it's an issue with the SECU regardless
- Door Lock Actuators : Even if they're totally shorted, they shouldn't draw any power unless the SECU says so. That's where the switching is done to send power to lock and unlock the doors. If there is power being leaked to them, it's again the SECU.
- Headlights Buzzer: That's controlled by the headlight switch. If there was a problem here, the headlight circuit would be drawing power and/or the buzzer would be on.
- Ground : The ground could be an issue. If an electrical circuit has an insufficient ground, it will actually draw more power from it's source to compensate. Ground is good.

Dealership wants $373 for a new one. Called a local wreckers, they have one compatible '04 Frontier. Unit if available is $40 from it. They also have an 01 and 03 in their sequestered section of fixable vehicles. A module from those is $90...

[Bow_Tied]

Are there any lights that stay on after the interior light battery saver kicks in, such as vanity mirror?

Is it possible that a door lock solenoid or switch could be drawing the power?

[Nd4SpdSe]

Not that I'm aware of, this is an Xterra, not a Pathfinder, no vanity mirror or glove box lights Interior lights, even if manually turned on, are suppose to turn off after a while to save battery. That being the case, it's the SECU's job to turn them off

I've isolated the draw down to a specific wiring harness. If there was an other draws, I would of came across them when pulling fuses, it would of shown up, especially if it would be on a different circuit.

For the actuators, here's something to learn you

An actuator is like an electric motor, when you give it power, it moves. Look at the actuator as, say, a lightbulb in your house. Say the the SECU is the switch on your wall for that light, and the car battery is represented by the 120v power coming into your house...

Now, the light normally goes on when you give it power, and off when you cut power; the switch controls that flow. One day, you notice the light bulb is glowing faint red, like it's getting just tad a bit of juice, but the switch is off. The trick is that you don't know if it's the bulb, and you're not allowed to change it. Tell me where the problem is.

[Bow_Tied]

RIght, so what I guess didn't know that your fuse pulling has eliminated that there could be a slight draw in a door lock actuator even though it is on this secu circuit.

[Nd4SpdSe]

Exactly. The SECU circuit controls the power flow to the actuator. Regardless of the condition of the actuator, it can't draw power that isn't there. It's the SECU that sends/controls the flow of power to the actuators.

[Bow_Tied]

What size fuse protects the secu?

[Nd4SpdSe]

There's actually 4; a 7.5a, a 10a, another 7.5a and a 40a. The second 7.5a and the 40a are the only 2 that are still powered while the truck is off

[Bow_Tied]

Interesting. I was wondering if the secu actually controlled full device power or rather signal power to relays.... thinking a relay somewhere might be having issues...

[Nd4SpdSe]

I haven't taken it apart yet, but according to the wiring diagrams, there's a only a few relays. I know off hand there's one for the rear defrost (which is controlled through that box). There may be some in the anti-theft and exterior lighting circuits that are controlled by that box (those circuits aren't causing the problem, so I haven't looked), but for most it's directly out of the SECU, including locks.

[Bow_Tied]

To make sure I understand, the secu interrupts continous power from various fuses for the items you listed. If all is working properly, the secu allows power to the list of items as called for with the ignition key in the on position or for a set amount of time based on the ignition key being turned off. Is that right?

[Nd4SpdSe]

To make sure I understand, the secu interrupts continous power from various fuses for the items you listed. If all is working properly, the secu allows power to the list of items as called for

Yes, exactly

with the ignition key in the on position or for a set amount of time based on the ignition key being in the off. Is that right

Depends; some is timed ignition off(interior lights), some is ignition-on based (exterior lights), some is ignition based with a timer (rear defrost) and some is on at all times (locks).

[Bow_Tied]

Ok, makes sense.

So, breaking that down....
ignition on only iterms (exterior lights, defog) if they have power when the key is off that would be a failed secu or a false signal from the ignition to the secu saying it is still on (can likely rule this out as I think you would have noticed?),
if any of the timed elements still have power after time out, then either it is a failed secu or the secu is receiving a false signal from the ignition.
If not the above, then each and every continous power item must be isolated from the circiut by fuse removal to eliminate them as the drain (which I think you have done). This should leave only the secu as the fault at this point, right?

ok, I re-read that and it may not be that simple, but you see where is was going in the elimination thing.

Is there current draw from the secu via the ground ?

[Nd4SpdSe]

So, breaking that down....
ignition on only iterms (exterior lights, defog) if they have power when the key is off that would be a failed secu or a false signal from the ignition to the secu saying it is still on (can likely rule this out as I think you would have noticed?) [...] the secu is receiving a false signal from the ignition.

Pending the relays on those circuits, but yes, indeed. If it was a false ignition source, other circuits would of been affected and noticed since that ignition source is shared.

if any of the timed elements still have power after time out, then it is a failed secu

Exactly since the SECU controls the time-out

If not the above, then each and every continous power item must be isolated from the circiut by fuse removal to eliminate them as the drain (which I think you have done). This should leave only the secu as the fault at this point, right??

Yep, that's both a start AND ending point. You need to start with that to find which circuits are affected to isolate those. From there, you need to break down that circuit again. Like for the SECU, there's 4 potential fuses, so it's a good idea to go back and work with those 4 again, but that's actually one of the more complicated circuits.

ok, I re-read that and it may not be that simple, but you see where is was going in the elimination thing.

Actually is it that simple. The hard part is not overcomplicating the circuit and looking for something that isn't/won't/can't be there.

Is there current draw from the secu via the ground ?

Current flows through the circuit, so you'd see the same value on both ends. For ground test, you'd would test for continuity, resistance or voltage drop.

[Bow_Tied]

Cool. Are we getting anywhere?

Current flows through the circuit, so you'd see the same value on both ends. For ground test, you'd would test for continuity, resistance or voltage drop.

I was meaning from the secu 'chassis' to ground.