Battery Dying Fun Times FJ62 (1 Viewer)

[wrc3]

So I have been having this battery drain which I originally thought was because of an old battery. After replacing that with a new one I realized I was only getting 13.3v at the battery when charging, so I replaced with a new Alternator. I now get 14v at the battery and about 14.4 direct from the alternator. Problem is now if the truck sits for 3 or so days the battery is dead. Like wont even click the solenoid. So I tried to measure the draw on the battery. Disconnected the negative terminal and put a mutimeter in line between negative terminal and negative post. Set the multimeter to DCA and only get a reading on 200u of .2. Which is a super low draw I would think. So what is killing the battery?

 

[BurntToast]

How old is the battery?

 

[wrc3]

Brand new. Under 2 months.

 

[vipergrhd]

Any aftermarket electricals like alarm ,radio etc.? Alarms are notorious for drains.

 

[KLF]

. 2 amps (200 mA) is still higher than it should be, I would start pulling fuses until the drain goes away so you'll know at least what circuit it's on. Should only be about 20-30 mA, just for the clock and the engine ECU.

GF's battery in her CRV would die if we didn't drive it every day, and I only measured a .5 A parasitic draw. Turns out it was an aftermarket remote start causing the drain, yanked it out and now it's fine.

What other aftermarket electrical devices are installed?

 

[wrc3]

So is 200u micro or milli amps? I read the 200u was microamps which I thought was super low. If it is milliamps then I can start pulling fuses. I am guessing the dome light or radio.

 

[OSS]

Also remember — whenever the battery is disconnected, the ECU has to learn your driving habits again and it takes time.
Never disconnect the battery if you’ve got a smog test coming up. Usually that will cause an instant fail.
The FJ62 is notorious for parasitic battery drain from the ECU, but killing the battery in a few days is excessive. Not right

 

[wrc3]

Ya it was dead it 72 hours. In the past I have let it sit 2 weeks and it will still (barely) crank.

 

[wrc3]

Well I went back out and now I am getting no draw when before I was getting .1-.2. I dont like troubleshooting electricity.

 

[wrc3]

Ok so I figured out it pulls 550 milliamps key off. If I pull the Dome light fuse it drops to 450 milliamps. Nothing else affects it except this connection (see attached photo. Once I disconnect this wire it drops to zero. So next question what does this wire do? BTW mine looks super suspect. About 8 inches up on the harness side 2 wires tie into one that then ties into this connection. Looks like previous owner did some interesting work.

 

[wrc3]

So it appears that is the alternator connection. And being that I just put in the new alternator, what are the chances the alternator charges my battery but then drains it when sitting?

 

[KLF]

The DOME fuse also keeps the clock running (IIRC).

There could be a leak in the voltage regulator of the alternator.

 

[wrc3]

Ya I found this page which actually has some good info on testing an alternator diode. So gonna check that tomorrow. https://www.autozone.com/diy/altern...o its purpose, an,itself or connections to it.

 

[RevISK]

Watching.
I also have a parasitic draw and I’d just assume you figure it out for me.

 

[60Works]

So it appears that is the alternator connection. And being that I just put in the new alternator, what are the chances the alternator charges my battery but then drains it when sitting?

Fairly high if its not a Toyota part. Anything from a LAPS is suspect. Sometimes diodes leak.

 

[wrc3]

This was actually a Toyota reman part. But who did Toyota farm the reman out to? No idea. Anyways I have to take it to my local dealer to get a warranty replacement.

I am still not sure I understand all the physics of it. Basically it is pushing DC to the battery when running but when it is off the diode causes a closed loop with the battery that self drains? Not sure I get it but whatever.