BATTERY GAUGE FLUCTUATES

Got a new battery for my '07 Tundra about a month ago. Went to start my truck the other morning and it wouldn't start, after a few attempts the battery pretty much died. First step was to check the connections, disconnected then reconnected both positive and ground leads. Truck started right up!
Since then it starts up fine, but the voltage gauge fluctuates a bit, it increases then decreases just a little from the baseline.

Could it be the alternator, starter or even the new battery?
Thanks,
Kurt

 

By what you describe my guess would be either the battery or the connections.

 

Take a pic of your battery and terminal connections

 

How many miles?

 

Hey all, thanks for the responses. Took my Tundra to the mechanic yesterday ...he tested everything, battery, starter, alternator etc., couldn't find any issues so it was likely poor connections so he reconnected and cleaned everything up. 100k miles.

 

Disconnecting and then reconnecting the battery and everything was okay was the clue.

 

Well, I disconnected then reconnected the leads myself...then the truck started right up, but the battery gauge/meter started fluctuating. The mechanic did the same but also checked the other leads, i.e. voltage regulator etc. I'd read that a fluctuating gauge could be due to a faltering alternator. Whatever the case, it's fixed...for now.

 

All you can do is watch it for now.But it sounds like it may be fixed.Good luck.

 

Thanks! Yeah, it's one of those things that sometimes there's no clear answer to.

 

Had this happen today. I drove it kinda hard on the way home. Noticed after i calmed down that the gauge was moving quite rapidly but only little movements. I came home and cleaned all my grounds and connections. I fired it up and it immediately died. Fired it again and it ran but really low idle. After a minute or so it leveled out. The gauge isnt moving now and is sitting just a hair below the middle mark. The battery is getting about 13.7 volts at idle. I'm hoping my alternator isnt on its way out.

 

That's about what mine has always put out.When it's really cold out it will put out 14 volts but only for a short time then it drops to about what yours is. When you disconnect the battery on these Tundras and start it up the first time they immediately die. Then they are okay. I have no idea why they do this but they just do. It sounds like you probably fixed your problem.

 

Mine is doing this too. Once I disconnect the leads from the battery and reconnect, it cranks but then dies. After a few minutes it will level out and be ok but it’s frustrating.

I wonder is this really normal or could by alternator be going out

 

It's normal for it to die the first time after you reconnect the battery. I haven't a clue why. I guess only Toyota knows why it does this.

 

Neither of my Toyotas die after the first start when disconnecting, they will however idle low due to the ecu relearning

 

Maybe only the earlier models do it. Both our 2007 Tundra and 2010 4runner do it. However I don't remember the idle being low. If anything the Tundra seemed high till I drove it a bit.

 

I replaced the battery in my truck about a month ago. Its a 2017 and it died on first start up after installing the new battery..sooo its not just the earlier models. I did not have low idle either. Maybe just luck of the draw?

 

Interesting I’ve owned two early tacos 97 and 2000, couple runners from same time, they all did the low idle for couple starts till ecu relearned. My 94 fzj80 does real low idle to point of almost dies till it has had few starts. My tundra does low idle for first couple starts but has never died. Either way it’s the ecu having to relearn everything

 

Hello I have a 2010 tundra limited with a 4.6 my truck battery gauge with hold 14 volts while I give it fuel but when I stop at red lights or idle it will keep dropping off until the truck dies I changed the alternator this morning it sucks big time and I crank the truck back up and it idle real low and about 10 mins maybe 5 mins and it died again battery gauge start dropping off and I would give it fuel it jump back up and then fall faster idk what else to do the battery was bought July last year

 

Its the battery brother.... I've killed off more than enough to know. I've yet to replace my alternator and I'm running without a skid plate for over a decade.

 

10-4 I’ll give it a try and I run with that skid on the bottom as well damn things just gets in the way

 

Main reason I just ditched it... it sits in my garage. It made a 20 minute oil change into an hour plus ordeal. Don't off road, except for those food vending trucks down the street.

 

Changes the battery this morning and it did not solve the problem wonder if the voltage regulator going bad

 

Every toyota I've had dies immediately after starting the first time after disconnecting and reconnecting battery. It's a relearning type thing.

Load test your battery to know if it's truly bad. Voltage doesn't mean much. Anything around or below 10v when you crank is bad.

 

It did not die immediately it was about 10 mins running at a idle in the yard I walked out to check on it my battery gauge was dropping I gave it some fuel and it climb back up then right after that when you come out the fuel when it dies