Mysterious Battery Drain - 2005 Tacoma

Hey, fellow Tacomians -

Hoping this amazing community can help me figure things out once again! When you turn off the truck with the lights on, I assume there is some mechanism that keeps it from draining your battery. I'm wondering if this might be my problem?

SITUATION
For the fifth time in as many months, my truck wouldn't start when I climbed in after work. Once again, my wife had to come give me a jump start. I drove it home and put it on the charger.

After the second time this happened, back in May, I took it to a repair shop assuming it was a dead battery or bad battery (it is still under warranty). The shop ran tests, confirming that the battery was good, the alternator was good, and that it was charging. Their report was:

- Unable to verify any slow crank or no crank issues.
- Performed a battery test.
- Battery is testing good.
- Performed a starting system test.
- Starter is operating normally.
- Performed a charging system test.
- The alternator is putting out 14v loaded and unloaded.
- Checked the connections at the alternator. They are clean and tight.
- Terminals ends on the battery are tight and clean.
- Checked the starter harness.
- The wires are clean and tight.
- Scanned for codes.
- Found security codes. Depending on which key I used.

- Being unable to duplicate the issue, cannot verify that is the issue

Whenever this happens, I get it home and put it on the charger and then it starts reliably for several weeks. The one common denominator I can think of is that whenever I arrive to a dead battery I often notice that my lights had been left on... I didn't look to see the first couple of times but it has been true the last three.

Is there some mechanism that could be going bad and allowing the lights to be draining my battery? Is there some other possible explanation for why my battery goes dead every few weeks?

Really appreciate any insights you can share.

Bradd

 

Your light auto turn off system may be bad. Check if the driver side door switch is functioning and if it is, and the headlights are staying on after you open the door with the headlights on it’s probably a bad BCM.

 

When batt is all charged up
turn headlights “off” and leave over night, or how ever long it takes to drain
What happens then?

any electrical mods?

 

Is it totally dead as in no electrical power at all?

Has it been checked for a drain with an inline or clamp on amp-meter?

I have seen batteries that test good but have an internal short and will drain themselves, you can test this by leaving the battery disconnected. If it still goes dead even if it's unhooked then the battery is junk.

 

Thanks for the reply! With headlights off, it starts up just fine in the morning. It takes several weeks before the problem recurs. There are no electrical mods.

 

Thanks, I'll check it out tonight!

 

It has power to lock and unlock the doors, and to flash the seatbelt/check engine/battery lights on the spedo when I turn the key.... just not enough to even try cranking the engine.

 

A couple issues mine was giving me. The clutch pedal switch was bad, high resistance. Instead of replacing, I bypassed it so I no longer need to stomp to start. I think automatics have a neutral switch. Then my starter solenoid was bad, rebuilt and no issues since.

Something else to mention, when I had a car with a autozone alternator, it had the exact same issue. After jump starting, it would work fine until it stopped charging again. Jump start, worked again for 6 months, 4 months, down to every other week.

 

Great info, thanks! I forgot to mention that this transmission is manual, so there is a clutch pedal switch.

 

Might be up your alley to find out what's going on. Also check after about 30 minutes since the vehicle has been turned off to catch your fuel pump turning back on to keep your fuel system primed.

-J

 

If the passenger door is opened before the drivers door the headlights will remain on. In other words the passenger door opening first cancels out the Automatic Off Feature.

There could be an issue with the passenger side door switch....

 

You’re right.
I learned this from experience.
https://www.tacomaworld.com/threads/do-your-head-lights-stay-on-you-might-need-to-know-this.373690/

 

That's really interesting! In this case there has been no passenger, but this is really good to know.

 

Checked it out and the headlights did turn off as I opened the door after engine shutoff....I felt very fortunate about that after googling the costs of BPM's.

 

That's sure what this is sounding like. How did you diagnose the problem and figure out the alternator was the culprit?

 

I didn't do anything to diagnose it. Just assumed it had to be the alternator. I had already replaced the battery, and swapped the 4awg battery cables for 0000awg cables and new crimp on battery terminals.

I believe it's a common way for an alternator to die. Is yours oem or aftermarket?

 

Get you one of those cheap voltage meters that plugs into the cigarette lighter so you can watch your voltage while driving, it should stay between 13.2 and 14.8v depending on temperature. If it drops below 13v anytime the engine is running you have a charging system problem.

 

Did replacing the alternator fix it ? Did you get another autozone or something else ?

 

Well now you done it. Here comes my autozone rant.

I bought the autozone alternator to replace the one the car came with, it fit & worked, for a short time. 9 months, 6 months, down to every other week it would stop charging until I got jump started, then worked like nothing was wrong. Pulled it out, brought it back for lifetime replacement warranty. Dude puts it on the machine, then says nothing wrong with it. I tell him what it does and I need it to work always not just most of the time. He says it’s working now put it back in. This gradually escalated into screaming 1/4” from his nose, I refused to back down. He finally caved and gave me a replacement. The replacement did the same thing, bring it back. Now there’s a female manager who said it shows I returned it for a refund. Luckily their part number sticker was still on it. She kept poking at the computer, then looked to see who gave me my supposed refund, ahhh, yeah, he was a bad employee. She did give me a replacement, I got rid of the car.

There was a time when an alternator was an alternator, not any more.

 

Thanks for the rant. Sounds like you'll stay away from Autozone - I know I will. Not sure if it helps anyone but I've found NAPA parts to be of good quality but if they give me options I always take the best level they have.