Is it my alternator?? 2012 CrewMax Tundra

Hello all!! New in forum,1st post, 1st question coming in hot!!!
2012 Tundra Crewmax 150k miles almost never had an issue (mechanically) I have searched the forum and web and think it's a bad alternator, but decided to share the details and have someone wiser than me confirm it. So here goes..
Red battery light in dashboard comes on Saturday...Sunday morning still on, truck starts, 10 minutes into my drive truck totally dies while driving. Zero power, not even emergency blinkers. Figured battery so went to Autozone and got new battery..(kid behind the counter tried to test old battery..unsure if it was dead, (or he was new)..ended up replacing it under warranty) Put in new battery on side of road, truck starts, drive home 10 minutes, in driveway notice abs and traction lights now on plus red battery light still on too. 30 minutes later, truck is dead again. Left alone Sunday. Monday morning multimeter with cables on battery shows 0 volts..remove cables and shows 4 volts..tried charging with shumacher charger..with cables attached, charger kicked off after 30 seconds, without cables it continued to charge. After charging, battery over 12 volts..attach battery cables and begins losing charge/volts rapidly..5 minutes later, truck won't start, everything is dead again. Using multimeter, checked all fuses, no issues (under hood and under dash) checked the 7.5 under dash visually too. 180amp main fuse looks ok plus got beep from multimeter when touched one end to metal by 180 alt fuse and other to fuse down the path. Also, with cable OFF battery, touched multimer to each battery cable and got the beep as well. (not sure if that even means anything but checked it anyway) Only mod is the trailer brake control that has been there for years. Also, Alternator belt looks good. No visible issues from above. Any thoughts? Anything else to check? Will bad alternator bleed volts from battery that fast? Thanks so much for any feedback!!!

 

Have your alternator tested? Could do the poor mans version at home with a multimeter to test output voltage. Only part of the equation though. These are hard to get to I understand in the 2nd gen trucks.

 

Just for clarification, after you charged the battery to 12V+ and you connected the cables to it, was the engine off or on? As far as you testing the battery cables disconnected from the battery, it tells you you have continuity (no break in the cables), but it doesn't tell you if you have a short. You can test the alternator yourself with the engine running. You should be getting 13 to 14.5VDC at the battery with the engine running. If not, bad alternator.

 

Thanks BlueCrush..engine was off when cables were connected and battery began losing voltage.I know it sounds odd. Nothing was drawing power, ignition not in acc mode, but when cables went on, the voltage dropped without the truck running. Thanks!!

 

Thanks Knabores..I may end up having to get on my back to test the alternator. Still trying to get her started to check the voltage. Just trying to exhaust everything before dropping her at the shop, as I'm not confident doing this job myself.

 

As the likelihood of bad battery cables is less than a bad alternator (unless you had rodents chew up the cables). I'm 99% sure it's a bad alternator. A failed diode in the alternator creates a closed circuit that drains your battery even when the engine is off.

 

Just a follow up..had her towed to the local Toyota Dealer (Surprise, AZ) this morning..got a quote for the replacement of the alternator. (Was shocked when it was a few bucks less than 2 other local repair shops) Hoping that's all she needs. Thanks to the Forum for the feedback as well as the info I gathered through researching on here!!!

 

I got rear-ended back in May. I got a new Taillight and continued to drive her while I was going around with insurance. The crumpled metal eventually cut through the smashed wires and shorted out.

I had the exact same signs. The truck was driving and then it stopped in the middle of the road. No warning lights, no dimmed lights, no slow accessories, etc... Part of replacing the alternator is dropping the sway bar and for some reasons the Tundra's will break the welded nut loose inside the frame when you drop the sway bar. If I may offer, take the awesome deal from Toyota to replace it. That welded nut thing would be their issue to deal with then.

 

All fixed?