Battery Light

I had a very strange thing happen today and I wanted to see if anybody had any ideas how to trace it or if they had experienced the same type of thing. I have a 08 DCSB with a manual transmission. I drove about 400 miles today with the last 200 pulling a trailer with a total of about 1500#'s. Driving down the interstate I noticed the battery indicator light flickering. Not blinking steady but just randomly flickering. It would go off for a bit, then flicker some more but never stay on steady. I assumed the alternator was about to go and I was 100 miles from home. Long story short. It continued flickering. A few times it stayed on solid for a bit and I thought here we go I am about to stop but then it would go out for a while and then start back flickering. I made it to my shop and let it cool off for about 30 minutes while I unloaded the trailer. I checked the belt and it was tight. They battery cables were tight and clean. Nothing visual at all. Well the truck cranked fine and no more light. 30 minute drive home with no light. Cranked it again after I got home. No problem. Check the battery and it was 12 volts.
I assume if the alternator was going out I would not have made the 100 miles home and the battery would not be fully charged.
Any ideas?????
Thanks

 

check the battery voltage while the engine is running to make sure the alternator is actually working. maybe take a look at your trailer plug/wiring. how old is your battery?

 

I checked the battery with it off and with it running. It was 12.3 not running and 13.7 while running. I pulled the trailer home empty and the light didnt come on but thats a good idea to check it. I will do that in the morning. I have only owned the truck about 4 months so I am not sure on the battery. I will check the code on it in the morning as well.
THanks

 

12.3v isn’t a fully charged battery.
You should do a load test on the alternator to see if it charging correctly.
I remember seeing the factory test method posted on here somewhere.
I’ll see if I can find it, if someone else doesn’t first.

The regulator in the alternator will provide a ground for the charge light.
This is what turns on the light, not the BATTERY voltage.
Something is providing a ground to the light. (My guess is the alternator)
And it should if it fails to output enough voltage.

I drove home 200 miles with a bad battery. Wouldn’t even crank the truck.
The battery light never came on. BTW, this is a BAD idea. Don’t do this. It is hard on the alternator.

 

12.3 and 13.7 are both low. Running you should see 14.4-14.1, lower than that your alternator may be on it’s way out. Give the engine a good rev to 2k or so, hopefully your number will be higher.

Even if the battery looks clean, the posts can become oxidized, they’ll look black or dark grey under the terminals. Brush the terminals and posts with a battery brush, see if your numbers improve. While the battery is disconnected, you can test how good the ground is. Attach one end of your meter to the ground terminal, then poke all over with the other end. Alternator body, anything metal on the engine, bare fasteners here and there. Good to see .7 or lower.

If your meter has a peak high and low voltage hold you can easily test how strong the battery is. Attach the meter to the battery, set it for peak low dc volts, start the engine. I typically see 10.4 on a new vehicle. 10.1 or less is weak. You can still do it if your meter doesn’t have that feature, it’s just not as accurate or easy.

If you have a good trickle charger you can let it go overnight. Then test again in the morning. And again later to be sure, like in a couple days.

 

13.7 is quite normal for 2nd gen Tacos with computer controlled alternators, 12.3 is a tad low for resting voltage(a fully charged battery should be 12.6 at rest). Mine runs from 13.2 on a hot day to about 14 on a cold day, has since it was new just depends on engine temp and ambient temp.
Another good test is turn all your loads on (A/C on High, Headlights on High, Etc) then check your running voltage, it shouldn't drop below about 13.2.

 

It seems as if Toyota doesn’t care about the voltage (so long as it’s 13.2-14.8), as much as the current.

I finally found the link - Here

 

This ^^

 

Have a look see at your battery's date code as well. It could be on the way out and might be wise to replace it just for the peace of mind, since you mentioned recently purchasing the truck.

 

Ok bunch of new numbers. Didn't trust my previous numbers because my meter is old and the leads may not have been making contact. Great reason to buy another one this morning. New readings. 30 minute drive to work. No battery light. Charge on battery not running but hot engine - 12.74. I let the engine cool for about and hour. Checked again. Not running - 12.73. Running 13.90. Running with Radio, Headlights, wipers and AC - 13.70.
The battery is stamped 12/18.
I did notice that with it under a load with everything on that it was dropping. It started at 13.70 but after a few minutes it was down to 13.68.

 

Thats good info right there. Thanks for looking it up!

 

.02 of a jump isn't terrible. Sounds like your battery is 2.5 years old, so I think that it's okay..at least can check that off the list.

 

Checked the battery and the alternator on the machine at the auto parts store. Both checked out good under load. I needed the truck today so I drove about 200 miles with 100 pulling a load. No light this time. I guess I give up until it happens again.
Thanks for all the help.

 

Just bring the multi-meter with you and check the charging voltage next time you see the warning light

 

It was on the passenger seat!
Along with some extra tools.

 

13.7 would be about normal on a drained battery that's sucking amperage during a charge. 14+ would be normal when the battery is fully charged and the alternator is keeping it that way.

 

There's nothing wrong with 13.7

 

Thats the easiest / quickest thing to try ^

 

Yeah I gave them a good cleaning when I had it out to get it tested.