Mysterious battery drain

I’ve been chasing a battery drain for almost six months now. I’ve had the battery and alternator tested multiples times and both always test good. I’m not sure how long it’s been doing this because previously I was driving the truck everyday and now, it only gets driven once a week at best.

If I don’t drive my truck for a week or so, it’s dead. I’ve done a ton of parasitic draw tests and the results vary. Sometimes the amp draw is 0.13 and other times it’s .03. No single fuse seems to reduce the amp draw though. As of yesterday and this morning, the amp draw has been consistent with .05 which is ‘within spec.’


This morning I tested the diode in the alternator and it passed within spec.


Side notes:
I have noticed that two times it has been dead, it was with a heavy snow or raining. I’ve read where the windshield leaks and will let water into the fuse box inside the cab but everything looks and feels dry. Also, my torque app has been showing a spike in voltage while driving. It will record the max value and it has been anywhere from 15v-18v for a half a second. I’m starting to get to the point where it’s getting passed my diagnostic skill level and going to take it in. I suppose I could toss on a new alternator for grins but I don’t want to throw parts at it either. @empty_lord or anyone else that has some suggestions, I’m all ears.

I will start a log to keep record of it:
05/30 - Battery installed @ 7:20pm
Amp draw - .05a
12.45v
SOH: 100%
SOC: 73%
CCA: 747
R: 4.02m-ohm

06/01 - 12:47pm
Amp draw - .05a
12.35v
SOH: 100%
SOC: 55%
CCA: 747
R: 4.02m-ohm
*started for 10min around 2pm*

Test drive at 6:09pm
Amp draw - .04a - removed aux fuse box
12.38v
SOH: 100%
SOC: 63%
CCA: 719
R: 4.17m-ohm

After test drive 6:44pm
12.72v
SOH: 100%
SOC: 98%
CCA: 742
R: 4.04m-ohm

06/02 - 7:10am
Amp draw - .035
12.37v
SOH: 99%
SOC: 61%
CCA: 708
R: 4.24m-ohm

Battery charge test - 06/02
Starting results before charge
12.42v
SOH: 100%
SOC: 70%
CCA: 740
R: 4.05m-ohm

2a charge from 3:37pm till 9:31pm
Results
12.94v
SOH: 100%
SOC: 98%
CCA: 761
R: 3.94m-ohm

Retest: 06/03 - 8:17am
12.65v
SOH: 100%
SOC: 98%
CCA: 754
R: 3.98m-ohm
**Battery installed at 10:00am**

Battery tested at 8:14pm
12.61v
SOH: 100%
SOC: 98%
CCA: 753
R: 3.98m-ohm
PROGRESS!

06/04/21
Restarted again this morning at 10:29AM
12.54v
SOH: 100%
SOC: 90%
CCA: 746
R: 4.02m-ohm
Amp draw: .030 without accessories
Amp draw: .044 with accessories

Drove to car wash and retested - 11:13am
12.91v
SOH: 100%
SOC: 98%
CCA: 749
R: 4.00m-ohm
Parked and everything back to normal including arming Viper.

Retest - 10:12PM
12.56v
SOH: 100%
SOC: 93%
CCA: 764
R: 3.93m-ohm

06/05/21 - Retest 12:26pm
12.47v
SOH: 100%
SOC: 78%
CCA: 766
R: 3.91m-ohm

Battery test - 5:34pm
12.50v
SOH: 100%
SOC: 83%
CCA: 771
R: 3.89m-ohm

Battery test - 10:39pm
12.47v
SOH: 100%
SOC: 78%
CCA: 769
R: 3.90m-ohm

06/06/21
Battery test - 11:13am
12.43v
SOH: 100%
SOC: 71%
CCA: 769
R: 3.98m-ohm
*good battery*

Battery test - 5:07pm
12.43v
SOH: 100%
SOC: 71%
CCA: 769
R: 3.95m-ohm
*good battery*

Battery test - 8:21pm
12.43v
SOH: 100%
SOC: 71%
CCA: 756
R: 3.96m-ohm
*good battery*

06/08/21
Battery test - 10:07pm
12.38v
SOH: 100%
SOC: 63%
CCA: 743
R: 4.04m-ohm
*good battery - RECHARGE*

06/09/21 - Test drive, parked at 8:40am

06/11/21 Battery test - 7:17am
12.32v
SOH: 100%
SOC: 53%
CCA: 714
R: 4.20m-ohm
*good battery - RECHARGE*

10:15am
12.32v
SOH: 100%
SOC: 53%
CCA: 717
R: 4.18m-ohm
*good battery - RECHARGE*

4:47pm
12.35v
SOH: 100%
SOC: 58%
CCA: 722
R: 4.16m-ohm
*good battery - RECHARGE*

06/13/21 - 09:46am
12.27v
SOH: 100%
SOC: 45%
CCA: 706
R: 4.25m-ohm
*good battery - RECHARGE*

06/13/21 - 12:12am
12.32v
SOH: 100%
SOC: 53%
CCA: 714
R: 4.20m-ohm
*good battery - RECHARGE*

06/13/21 - 09:46am
12.27v
SOH: 100%
SOC: 45%
CCA: 706
R: 4.25m-ohm
*good battery - RECHARGE*

06/13/21 - 06:55pm
12.33v
SOH: 100%
SOC: 55%
CCA: 718
R: 4.18m-ohm
*good battery - RECHARGE*

06/14/21 - 02:39pm
12.31v
SOH: 100%
SOC: 51%
CCA: 701
R: 4.27m-ohm
*good battery - RECHARGE*

06/19/21 - 02:27pm
12.29v
SOH: 100%
SOC: 48%
CCA: 695
R: 4.30m-ohm
*good battery - RECHARGE*

06/20/21 - 05:58pm
12.28v
SOH: 100%
SOC: 46%
CCA: 698
R: 4.29m-ohm
*good battery - RECHARGE*

06/27/21 - 05:47pm
12.43v
SOH: 100%
SOC: 71%
CCA: 755
R: 3.97m-ohm
*Good battery*

06/29/21 - 09:13pm
12.36v
SOH: 100%
SOC: 60%
CCA: 728
R: 4.12m-ohm
*Good battery - RECHARGE*

06/30/21 - 10:58am
12.34v
SOH: 100%
SOC: 56%
CCA: 714
R: 4.20m-ohm
*Good battery - RECHARGE*

2018 Silverado 1500
Sitting for two weeks
08/14/21 - 09:28am
12.22v
SOH: 100%
SOC: 36%
CCA: 714
R: 4.18m-ohm
*Good battery - RECHARGE*

08/31/21 - 09:31pm
12.51v
SOH: 100%
SOC: 85%
CCA: 750
R: 4.00m-ohm
*Good battery*

09/02/21 - 08:06am
12.34v
SOH: 100%
SOC: 56%
CCA: 718
R: 4.17m-ohm
*Good battery - RECHARGE*

*Started and moved - 2min*
09/02/21 - 08:11am
12.89v
SOH: 100%
SOC: 98%
CCA: 750
R: 4.14m-ohm
*Good battery*

 

I have been in the same boat with my ‘03 since I have owned it. I initially thought it might be from the rats nest of trailer light/camper top wiring iterations. I’ve cleaned that all up. Everything tests fine, though electrical things remain a bit of voodoo to me. It has been to three mechanics, all of whom tried to diagnose but found nothing.

Sometimes it is dead overnight, sometimes it holds a charge for a week. I can offer no help, but eagerly follow your hunt.

 

Have you recorded humidy, temps, times, sunshine, clouds during parasite testing?

I assume you do not have garage so your truck would be 100% exposed to the elements 100% of the time, and those factor in which could help you see a correlation between High Draw and low draw circumstances.

High draw may be on Hot, Dry day.
Low draw my be on Cold, wet day.

Data points to see the trend!

What happened about 6 months ago? Install aftermarket radio?

This is the only thing "electrical" that's on your build thread from about 6 months ago.

See if you can unplug this, and then do draw testing exactly how you were before.

 

So during the parasitic draw test, you remove each fuse to isolate the circuits. By doing so, I’ve removed the radio, remote start and aux mirror circuit with no change in amp draw.

As far as weather goes, it seems to be dead on colder/humid weather but I haven’t been watching it that close. I do not have enough garage space, so yes, it sits outside.

 

Best of luck with this - I've dealt with this issue on a different vehicle and know your pain. Hope you get it figured out.

 

Have you replaced the battery? I’ve had sulfated cells cause weird drains but always pass

 

Yup, I’m on my third one lol. The last one was replaced in 12/2020 so it’s the only six months old. It’s tested good on multiple testers.

 

Check and clean all grounds and battery connections. These are the obvious which I assume you’ve done.

Still think its the Alternator based on the spikes. Maybe disconnect the battery fully after its charged and bring it in the house until you need to start her up. This should rule out a phantom drain during the week.

Original Alternator? Might be time regardless if its something else. Iirc you have 270k miles on her?

 

Yes, all cables are squeaky clean. Is their a diagram for all grounds? All obvious ones are clean and tight.

Right now, the battery has been disconnected since yesterday afternoon after the parts store gave it a 100% charge and it passed with flying colors.

I still may think I’ll throw one on there since they aren’t that hard to change nor expensive. She’s got just about 190K and it appears to be the original.

 

Grounds:
1) Next to Battery

2) Fire Wall near Heater Core entry/exit

3) 2 on either side of backside of engine between Firewall (skinnys)

4) @FrenchToasty favorite ground on the Driver Side Block down low just below the Front o2 Sensor (Thicky).



3) and 4) aren’t on any of the FSM Diagrams AFAIK.

Your Alternator is Ground to the Block so pay attention to clean up the mating contacts and bolts/nuts. Maybe use some NoAlox.

 

Your chase and processes of elimination is on target and my first thought would have been alternator diodes leaking to ground. As previously mentioned and before you take it in and pay someone to start the process all over again, I would pull one fuse at a time and see if the problem shows up as a last effort.

Good luck with your search.

 

If it were me, I’d use one of these Hall effect current clamp meters than can measure down to a milliamp.

But then again, I’m just trying to find a good reason to buy one.

 

Are you wearing a G-String in this pic?

 

More often than not, it's the aftermarket security system/remote starter. Dash cam "parking mode" capabilities are the other. Take a very detailed look there and let the truck sit with it disconnected.

 

I’ll never be able to look at an A-26 the same way again…..

 

Traced mine down to trailer harness wiring for my 7 pin. Could be the trailer brake controller. These things are aftermarket and were not attached to the factory fuse box. I pulled the hot wire to the 7 pin trailer harness wiring and the draw dropped from 0.12 to 0.03. Haven't had a dead battery since. Haven't figure out which component is the culprit, but it's likely the aftermarket backup camera that was using the trailer harness +12v for a power source. I wired it into the backup light trigger for now so that it's only on when I'm reversing.

 

I appreciate the advice. I’ve lost count on how many times I’ve done this test but 10 min ago, I pulled each fuse one by one again monitoring the amp draw. No single fuse drops it except the 15A dome light fuse. It holds steady at .05mA and when I pull the dome light fuse, it drops to .04mA so not a huge difference. Once I reinstall the fuse, it bumps up to .09mA (radio is getting energized I presume) and then after 3-4 seconds, it drops back down to .05mA. I’ve left my multimeter on it for 30min now and it’s holding steady at .05mA with no change.

My truck does have an aftermarket trailer harness on it that I can see if I can do the same and remove the hot wire but according to my tests, it’s not getting a big draw from the battery or at least when I’m looking at it.

 

The Elec Wiring Diag(EWD) have grounding point drawings.
I would also suggest checking your cabin gnds especially kick panel area, if you haven't already.

Just curious if you ever fixed the one by your battery ?
Multiple electrical issues first gen 2001 Toyota tundra

@RainMan_PNW made EWD's available in General Discussion Section for 1st Gen and udder gens....Ultimate Wiring Diagrams Collection | Toyota Tundra Forum (tundras.com)

 

I think I will call the two shops and see if they have a way of double checking their work to make sure it isn’t something on their end. Both came with a lifetime warranty on parts and labor.

 

Also how did you wire your light bar? Is the relay connected to switched or constant power?

 

Here are few additional findings:

When removing the “CARGO LP5A” fuse, the draw goes up to .06mA. Not sure if that is normal?


This is looking the carpet behind the E-brake. It looks like it’s wet at the top but it’s dry. We have had heavy rain the last few days so I would assume if it was leaking, it would have done it now.


Looking at the brake pedal assembly etc. They have some surface rust.


Appears to be the OG alternator:

 

Separate fuse box with separate fuses. I have removed those fuses and no change.

 

Yes I did get that fixed, thanks for the post. From my brief google-fu, it appears bad grounds don’t cause battery drains? I only briefly searched that so if that is incorrect, someone please correct me.

 

No closer, but thank you.

 

Good grounds will help with charging and electrical efficiency.

 

Might be a good time to peel back the A-Pillar Gaskets and unscrew the metal plate underneath which is easy. Inspect those 4 clips and associated gaskets. Mine were failing. Not sure if they ever leaked, but they were on the way out. Used Butyl Tape to seal up. I did this after a new windshield. Check my build page for pics.

 

I’ll take a look. I think this week, if the weather holds, I’ll remove that cowl under the wipers and put a bead of marine silicone at the bottom to eliminate that, just in case. I hooked up the battery tonight and I’ll make a log over the next 2-3 days on the battery activity.

 

Just an FYI:

I had this same problem with my old F250. All stock except a chip and remote start (even radio). In the winter, the truck would need a jump if it sat more than a week. This went on for a year until one day the alternator failed and the idiot light came on.

It had passed all the tests without issue as well. Haven't had any problems since replacing the alternator, even after it sat for a month.

Best of luck - it's a PIA to have to think about if it will start when you go to use it.