Mysterious battery drain

Looks like wiring for an aftermarket trailer brake converter

 

This....

 

Did the parts house insist that you buy a new alternator on the 2nd or 3rd battery replacement?

 

You are correct. A member on the FB group posted the same wire but his still had the tag on it which read “trailer light power fuse.”

I checked it but it isn’t drawing any power. I have it disconnected for now for safety measures.

They did not, but I’m leaning towards it. I charged up my battery tonight and I’ll test it tomorrow again. If it reads the same tomorrow or close to, I’ll throw an alternator on it.

 

Have you checked for the box. It intercepts the brake lights and turns. It can do weird shit like drains and other stuff when they go bad


In doing the main power won’t fix the issue if the issue is with the other circuits

 

I disconnected at the box by the taillights with no difference in amp draw. I’m beating my head against the wall on this one.

 

Unplug the alternator and disconnect the post overnight?

 

Hmm. Sadly it would appear you’ve got a nightmare draw. When you check it, leave the amp clamp on and leave the truck for an hour or so untouched. Check the reading after it sits for a while. Something ina security system when it sits idle may be your issue

 

IF you do this, DISCONNECT THE BATTERY FIRST. then reconnect after the main power wire is taped off. That sucker touches anything that’s grounded and you get to pulley whole fuse box apart to replace the alternator fuse

 

^this.


It's common sense to me (and most working in a shop) but I should have mentioned it.

 

I forgot to to someone and I felt so bad afterwards I replaced the fuse for him. It’s common knowledge for us. But not everyone

 

First off, all good information and I really appreciate everyone’s feedback/responses. I have charged up the battery tonight and it’s showing 12.94v. I’m going to let it sit overnight and retest it in the morning for any voltage loss.

If no changes, I’ll reconnect the battery with only the alternator connected. I’ll retest the battery for voltage drops.

Lastly, if it passes both tests, I’ll roll the dice and put an alternator on it. What I don’t understand is the massive voltage drop I am getting with only a .03-.05 draw. It doesn’t add up that that little of draw is draining the battery that quick.

 

We used one like that during the war to interrogate the enemy....

 

She’s large and in charge...lol.

I think I sold this unit to my dad when I worked at Napa back in 2008-2009. Still works like a charm but it’s a pain to store. I think I’ll go buy the $50 at Wally World I’ve been eye balling this week.

 

PROGESS!!

Or at least I think so. Again, I disconnected anything that was aftermarket connected to the battery directly. I installed the battery at 10am this morning and rechecked it just now and it’s only lost .04v in ten hours! I was going to check the amp draw but decided to not disturb it until I check it again after letting it sit overnight.

The only thing I changed today was the positive battery terminal. Like I said previously, the OEM was loose and wasn’t getting super tight anymore. I could snug it down tight but if I put enough pressure on it, I could get it to spin. Could that have been causing the issue?




I also bought new relays for the aux lights because they are looking pretty crusty. I’ll get them put in tomorrow and hopefully that takes care of the small amp draw from them.

 

That terminal looks rusty/crusty and could very well be a problem. Everyone should clean theirs up and put some NoAlox on for better Vibes and Protection.

 

I cleaned mine awhile back after it got corroded so this is after the cleaning. For the $2.86, I’d say just replace it. The new unit is really heavy duty and a much better design.

 

Checked the battery 24 hours later and it’s looking promising. Installed the battery at 10am yesterday and the results were:

Beginning of test - 10AM
12.65v
SOH: 100%
SOC: 98%
CCA: 754
R: 3.98m-ohm

Retested at 8pm
12.61v
SOH: 100%
SOC: 98%
CCA: 753
R: 3.98m-ohm

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

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

Literally the only thing that has changed was replacing the positive battery terminal. I will retest it again tonight and tomorrow to see if it’s ‘fixed.’

 

There may have been enough resistance in the original cable end to prohibit current from flowing correctly. So, you weren't "really" charging the battery fully each time...
It's like you gave the positive cable Nasal Rhinoplasty. Now it can breath again...

 

Go ahead and do the Negative Side for the Ying/Yang Victory.

 

That actually crossed my mind. I’d have to snip the end off and install an eyelet.

 

So in four days, it’s lost a total of .53v. There for awhile, the volts stayed pretty consistent. Does this seem like a normal drop in this time frame? I have not started it, just let it sit. I have logged all my battery testing results on the first post for comparison.

06/04/21 - After 35min drive
12.91v
SOH: 100%
SOC: 98%
CCA: 749
R: 4.00m-ohm
Parked and everything back to normal including arming Viper.
*good battery*

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

 

eeesh, I hate to say it but I don't feel great about seeing 12.38 volts after just four days. I would expect a healthy system to show about 12.7 volts for days, maybe dropping to 12.5 or six after a week or two.

I may be splitting hairs but 12.4 or lower after four days makes me nervous. Did you try starting it to hear how it sounds? Is it not dead as mentioned in your first post?

p.s. Good work on replacing the pos cable. The cable and terminals are wear items that can be revived but often they should just be replaced when 20 years of hot, under-hood conditions have left them for dead.

 

It fired up no problem and sounded strong. I wish I had a reference to compare it to. Right now, I’m just happy to see the progress it has made.

 

@SouthPaw
I learned of a possibly source of the power draw. Today I picked up my 2002 Tundra from the shop for some completed work. The battery was dead. I was annoyed because this has been a thing with my Tundra. I previously thought it was a short in the radio.

Today, the mechanic jumped my truck and immediately looked at the little cargo light button that was in the "on" position. He said that button is often accidentally activated and is a source of power drain and dead batteries. It is located right above the hazard light button, just visually behind the gear shift when it's in drive. It's very easy to accidentally press, and in the day you'd never notice it is on. And it just runs down the battery...

You might look at that.

 

Another member mentioned earlier the headlight switch. Leaving it in the on position draws current for a relay (towing relay, as I recall) with the key out. Yes, the headlights are out, but that relay is energized. You’re fine if you drive it daily, you’re fine over the weekend, but after about a week of being parked, it’ll be dead.

You can also simply install a battery disconnect switch. Not exactly convenient, but effective.

 

Appreciate all the advice guys. I’ve been keeping a log of my battery test results on the first page of this thread to monitor patterns. Most recently, it sat for 4-5 days and it stayed steady at 12.30v. I decided to drive it today and it fired right up within two cranks. Either I fixed something I didn’t know I did or the positive battery terminal was the culprit. I plan on parking my other truck for a bit and start using the Tundra as my primary for awhile.

 

I leave my headlight switch and cargo light in the on position for many days at a time with no battery issues.

 

To speak to that, I always turn them off. I’m used to the auto lights on my other truck but my Tundra, I always remember to turn the headlights off.

 

The headlights will turn off when the door is opened and the cargo light is on a timed delay. Haven't had any issues with these but they certainly could be sources of malfunction if relays went bad.