Random complete loss of all electrical power overnight

[Stevalli]

Hi everyone! I am new here, but I am finally tired of putting off getting my Tahoe fixed. It’s a 2003 5.3, and for the past year and a half has been giving me the strangest electrical problem. Basically, it started when the truck sat for about a month because my window got smashed and I just didn’t drive it. Once I fixed it, I charged the battery up and everything seemed fine for a few days. I drove it every day, and then one morning I go out to start it and there is nothing. No starter, no dome lights, no dash power… nothing. I wasn’t sure if something was left on, so I charged the battery later that day and put it back in. Again, completely fine and normal for a few days and then one morning nothing. I eventually replaced the battery because it had been a few years old, and the same conditions happened to the new battery too. The alternator is a few years old with probably only 20k on it (oem).
Fast forward to today and I’ve pretty much let the truck just sit. I was stumped and my motorcycle and other cars are here for me to drive, so I put off fixing it. But I went out yesterday and bought a multimeter to try and start figuring this all out. When put in ground line between battery and cable, the multimeter initially reads a little over one amp, but falls in big jumps and eventually reads 0 draw. Again, the drain was completely random and it was big enough to suck all the life out of the battery, so I have no clue how to go about addressing it. Any help would be greatly appreciated… thank you all!!

 

[OR VietVet]

Welcome to the forum from Oregon.

Do you have an alarm system on vehicle?

If can get the draw that big to stay on and start pulling fuses, you can diagnose that circuit. Are the ends of cables completely clean and free of corrosion and no corrosion down the cable in the insulation?

 

[Stevalli]

That’s really where I’m stumped… I have no clue what is triggering this random depletion, so it’s hard to know when it will happen or when I’d be able to measure it on my multimeter. I did pull off the terminal connection covers and clean them off on my last go around with this, and that didn’t seem to help. Maybe it’s an issue further down the power cables? Id like to know for sure before I go start replacing things since funds are a bit tight haha

 

[Stevalli]

As far as alarms go, it’s only what the car came with from factory. Aside from speakers, there isn’t a single non-oem part in the truck

 

[OR VietVet]

That over 1 amp draw is too much. Rule of thumb, years back, was 50 milliamps or lower and now I think is more. If you start by checking it each day and get the initial 1 amp draw that goes down, then you have a pattern. Then start by unplugging the alternator and see if that 1 amp draw is still there the next morning. If is gone and then plug back in and it comes back, well there you go. You can also unplug other components and see if that effects it and it will take a while but can narrow down the problem.

The cables will not cause the draw, unless they are crossed somewhere down the line, but can cause a loss of voltage needed to turn the engine over.

 

[Stevalli]

From what I understood, the initial spike is normal when you close the circuit with the multimeter and all the systems cycle. It only reads that high for about 10-15 seconds, after which it drops to essentially zero (every now and then it will flash .01). From that it would seem like everything is normal, which aligns with the fact that the car only randomly loses power.
Maybe this truck of mine came to life and is playing pranks on me idk, but even if there is something that intermittently draws power every few days, it’s hard for me to figure out what could pull so much power that there is nothing left at all.

Again, my knowledge on electrical is very elementary, so if this could be the result of some sort of grounding, shorting, or some other issue, I would need some guidance lmao

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Fless]

Can you show us a pic of the ammeter you're using, with the scale selected that was used when the ".01" value flashed on and off? Perhaps also show how the cables were connected (plugged in) to the meter?

 

[Stevalli]

Thank you to those who have replied so far. The multimeter was set to its 10a setting. I know that the multimeters fuse is good because it initially reads high when the computers systems cycle, but it falls to a very low number. I was worried to put it to the 200ma setting because of that initial spike being above 200ma, so I didn’t know if it would blow the multimeters fuse (but I did think of tying the system together with jumper cables to get past that initial spike, then attaching multimeter and disconnecting jumper cables. Not sure if this would work like it does in my head).
The past couple days I’ve been driving the truck around, paying close attention to check the batteries voltage at different times. I disconnected the battery last night, and it fell from 12.56 to 12.46 overnight, so now I know that this new battery I bought isn’t in the best shape anymore. I plan on leaving the battery connected tonight to see the effect it has.

 

[Stevalli]

 

[Stevalli]

A few things to note…
I’ve checked that the alternator is charging at exactly 14 volts, so not over or undercharging to my knowledge.

The two things I’ve noticed so far in these two days of driving that could be remotely close to a potential cause are:
1. My gauge cluster - Not only does my instrument panel only intermittently have power to some of its lights (gear selector lights only sometimes light up, parking brake light sometimes works sometimes doesn’t), but there is also sometimes when the high beam indicator light stays extremely dimly lit at all times. The thing is, these problems were present for quite some time before these major issues started, so I never really thought of it as a cause for such a major battery drain.

2. Now this one is extremely random. From what I believe, around the same time the car started having these problems, the siding to my seat that has all the power controls kinda fell off. The screws must’ve come out, and sometimes if I’m not proactive about putting it back in place it hangs. The reason it didn’t get fixed is because not long after it happened, these large problems started coming up so I was focused on that. So now that I’m thinking about it, I’m wondering if there’s a chance that those nights that the battery was completely killed, maybe the siding fell and got squished by the door, activating one of the switches all night long. When I get home I’m going to find a way to keep it in place, but from here on out it’s going to be a matter of waiting for the big loss of power to happen again. If it doesn’t, maybe that was what was happening? But my thinking is once whatever seat movement that was getting pressed reaches its limit, the motor would no longer be drawing power, or it would at least not draw so much that it completely levels out the battery. I have no idea, but that is about all I can think so far.

I know figuring all this out on a pristine battery would be better, but I would hate to smoke another new battery by drawing it all the way down if this was to occur again.

 

[Farmboy666]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

Do you answer every post you can get to with this same lame question?

 

[Joseph Garcia]

Do you answer every post you can get to with this same lame question?

Already replied to you Clown.

 

[OR VietVet]

Do you answer every post you can get to with this same lame question?

Do you use the same "lame" screen name on every forum you have not been kicked off of yet? Averaging 1 post per membership month means you gotta be trolling elsewhere.

 

[Fless]

Already replied to you Clown.

You should add a question to your posts so at least the criticism would be accurate.

 

[Matthew Jeschke]

You're on right track more or less.

I'm sure you've checked this... But make sure you have a GOOD connection from battery to battery cables. It can be you have a break in those power cables under the hood somewhere leading you to this symptom. It would drain the battery, and be dead as a door knob sometimes when trying to start it. Problem would get worse as cable degrades and bad grounds / power connections do really funny things. I'd do a continuity check from battery to starter... (can take battery out). best if you have somebody help you hold test probes on. Then wiggle that wire where ever you can. Inspect closely too. Do same for alternator to battery terminal.

One thing while you're at this, is to check all your chassis ground connections. Clean and service them. I don't have a diagram... from memory...

- Engine block to battery
- Front frame to battery
- Alternator to battery
- Frame (driver side?) on body mount

There's a few more but those are ones I recall. They should be under 1 ohm (or darn close to). You'll put one lead of volt meter (ohms setting) on negative battery... other lead you probe those points.

I've never tested an ignition switch but venture if it's intermittent it could drain a battery and or give a similar symptom?

Might not hurt to measure Alternator ripple while you have your meter out. Why not... I don't think symptoms you describe could be created by this but since you're learning. flip volt meter to Volts AC. Put one lead on on battery negative, second lead on alternator case. You want to see that under say 50mV w/ truck running. FYI ~ It can wreck a battery and or make electronics run really oddly if there's too much AC current getting by the rectifier in alternator (alternator going bad).

If you need to check draw of various circuits (haven't found problem already)... FIRST, turn off truck... Disconnect positive battery terminal... put your volt meter to amps... connect one terminal to the battery, connect the other to the battery cable. DO NOT START OR DO ANYTHING WITH TRUCK. You may also want to make sure your meter is fused (fuse inside of it). Now with truck off (IGNITION OFF) you shouldn't be drawing much if any voltage. You should also wait 15 or 20 minutes (doors closed) to do this test. See what your current draw is. I'd venture it should be quite minimal... Like less than 200mA... if otherwise, then start testing circuits in a similar way.

Hook back up battery... make sure truck is sleeping (can look on youtube to learn more). Go under hood, and start unpluging fuses. Measure current across fuse terminal to see how much current is being drawn. Eventually you'll see where the bad circuit is... Then let us know... I or somebody else can locate circuit diagrams for that fuse.

Electrical is really intimidating but basic troubleshooting is easy... and once you get hang of it, you can typically do it in a matter of minutes to find the bad circuit.