Tundra's Voltmeter Reading Up and Down Intermittently

AGM batteries need a higher voltage than 13.8-14.0v for proper charging.

You can do the Ford or GM diode replacement for the charging system fuse to bump it up .5v where the AGM battery will be happy.


Fluctuations are either alternator, battery or possibly wiring (sense wire for voltage regulator).

 

No fix here. Been driving it like this since my post and so far nothing hinky or weird has happened yet. Still fluctuates periodically.

 

Your back!

 

I mean, I technically never left. Just got really f'n busy and went off on a tangent.

I thought about popping in during the holidays, mostly because I swear I saw @Professional Hand Model 's truck while driving thru rural AL on the way to see my folks.

I won't be in posting a helluva lot in the next few weeks, plate is full. But since I actually did something to the truck, figured I'd pop back in. Sad I'll never know what 20 of the 21 notifications I had were. they must vaporize after a month or two

 

Might be? I did just obtain some custom made bed sheets with Alabama Cotton.

 

You can come back to them.


Glad things are well, but just busy. Busy is good.

 

Thanks! Got 1st shot Friday before last. Next one April. Work won't let anyone come back until they get shot. I need to get back so I can be doing less work again. They work my ass off when I'm remote.

And that's a big fat nope on the 'show all'.

 

The grind always grinds.

Oh...

 

Well fella's...it looks like the AGM battery was the culprit...ive been driving my truck more frequently (usually am driving the work truck around) and voltage is staying right at 13.8 when driving and around 13.5 when idling...not seeing fluctuations on the dash voltmeter. Tundras really dont like those AGM batteries...never again!

 

Sort of chasing a similar issue and I believe it is another bad battery from CRAPA. I don’t think their batteries are what they used to be but I’m betting that’s my problem. Did the same tests as you and will try and get my alternator tested sometime this week through the battery tester.

 

At least you all are getting some reading. I just got my 2003 access cab delivered across state lines today and the battery was dead when trying to get it off the trailer. Ran to O'Reilly's and grabbed a new battery and the truck fired right up, but the gauge is "below" zero.

 

13.8 is too low for AGM batteries. Look into the ford/chevy diode mod (.5v increase) or there is an Australian company that makes an adjustable option in .2v increments (can't recall the name at the moment).

 

Yeah. I used to see ‘group buys’ for these AGM all the time on this site a few years ago.

One guy in particular didn’t even own a Tundra. Don’t see as many doing them now as the reality has set in for most who didn’t do their homework. Thank you for reporting back.

 

Maybe the condensation on your bezel has broken the gauge?

 

How many miles on your truck?

 

I was thinking it was just a dirty cover, but now that you mention it, I’ll wipe it down and take a closer look.

The interior was pretty dirty when I got it yesterday. The entire cab smelled like that awful artificial “freshener.”

 

Yeah I saw the “HKM” one or whatever from Aus, I did the GM diode but it was only giving me 14.2 max...honestly I’m over the AGM phase...thought it was suppose to be maintenance free lol, requires a lot more maintenance than a lead acid IMO

 

Of course, we all need to help each other out, this is a wonderful source of knowledge. And I appreciate you for giving me the suggestion!

 

Almost 189K.

 

Not sure if what I’m about to say is still relevant, but I had the same thing happen as @speedtre where my battery meter was reading low. But to add, my battery light was on. Drove it home and the next day truck struggled firing up. Went inside to let it warm (pretty cold day) and came out after about 5 mins and it had shut off. Turned out being the alternator. It had shorted out internally.

 

Yeah. Reaching the Alternator Useful Life around 200k miles. Mine (brushes) were out of spec at 171k. Still running well, but she could have gone any time by the looks of the brushes.

 

293k mi, still original alternator. 2006 2wd dbcb. Bought a Denso reman., just waiting for the original to fail.

 

Whats your secret?

 

Wish I knew, same 02 sensors also. Bought some new Denso 02 sensors and going to replace soon.
I've soaking them with PB plaster hoping for a easy swap.

 

Not uncommon for cars that smell musty due to water leak or, less often, rodents. If you find it's water/mildew, see here.

 

Are the alternator brushes replaceable? Without major pain.

 

I’d consider it Agony Level 7.5 out of 10 if doing it from the topside. I’ve read you can get it done from under and the side wheel well, but am not experienced in that method.