Charging / Alternator Problems

Hey Gang. I have a 2005 Tundra AC. For a few months now I have noticed oddities with charging, where there might be a low charge with Battery light, and sometimes other lights. It has happened intermittently but then went away.

Last night nearly every light on the dash was on, including 4WD and related lights, windows would not roll down and no headlights, but the truck would run. No charge going to the battery via multimeter test. So I had a new alternator, and I put it in. Same problem. Initially thought I had a bad new alternator, but was not sure. Checked connections quickly, but did not notice anything.

I had the OLD alternator bench tested at O'Reilly's today - it tested perfectly - so I have some other issue.

I guess now I need to check the full wire coming from the battery to the alternator, but has anyone had issues like this? My battery is an AGM and less than a year old, and it is at 12 volts when I start the truck and it starts fine. When I could run a code check, I pulled no codes.

Here a picture of my dash when the issue is going on.

 

Is the alternator belt properly tensioned?

 

Check your connections for corrosion or damage. Perhaps the sense wire between the alternator and battery terminals is bad/damaged.

 

Have you checked the Alternator fuse? it is usually in one of the boxes in the engine compartment, if tow package it'll be a 140amp, if not it'll be a 100amp. mine is the # 48 fuse. Hope that helps

 

I have checked the tensioner. I’m gonna take the cable off tomorrow and check continuity on it. I did check the fuse it’s 140 amp and it seems to be working and looking OK. Thanks for the help guys.

 

You mention you have an AGM battery. Did you do the necessary upgrade on the ALT-S fuse to ensure the AGM battery is getting the added charge it needs to maintain proper charge and health?

If the answer is "NO"....

Did you have your local auto parts store test the battery to ensure it's functioning properly?

If the answer is "YES" ....

Check voltage at the positive battery terminal while at rest and while running with a DMM or voltmeter. Check all your cables, tug on them really good to ensure nothing is sketch or frayed or loose, including the small jumper from the battery to the engine bay fuse box that's critical. Check all fuses in that fusebox related to charging, including the pain in the ass to deal with 140A you checked, test for continuity anyway, I've read a couple threads here about it getting flaky on people. Confirm all grounds in the engine bay to make sure they're tight, or temporarily add an extra ground or two.

Last but not least, I don't see a location in your user info/profile. If you're in a corrosion-common state, check bulkheads at the firewall inside and out to look for corroded pins or similar damage, in the event none of the above turns anything up.

 

AGM Upgrade: No. Can you please explain what upgrade for ALT-S is needed? I am not following this.

I have not had the battery tested, but will. I charged it back up to full volts, so what test would be done?

I will be going through all cables tomorrow morning / testing for continuity.

I am SoCal / San Diego, so corrosion is minimal here but truck was prior WA State truck, but was pretty clean on that front, but will check.

 

https://www.tundras.com/threads/wha...-gen-tundra-today.2558/page-1082#post-2404302

Battery is voltage and amperage produced from the combination of multiple cells, not just straight up voltage. Cells can go bad, become inefficient, become damaged from not regularly receiving correct charge, I believe it's 14.6V with typical AGM? I think stock only allows 14.2, but maybe I'm wrong. I can't recall. Just remember this from that thread:

Anyway, not feeding a battery what it wants/needs/expects over a long period of time ... leads to early failure in my experience.

 

Also see: https://www.tundras.com/threads/wha...t-gen-tundra-today.2558/page-875#post-2136022

And to save hunting the GM p/n if you don't want to order from down undah:

 

Thanks a lot.

I took the AGM battery out and put in a normal battery. Tested directly at the alternator - have great current. Tested all fuses, all good. Tested voltage drop from battery to alternator - positive and negative - no issues.

Note, when I put the normal battery in and started it, it showed charge for about 5 minutes. Shut off, put the truck back together, and it came back to the same problem.

Also in the midst of this, I have a Christmas tree of lights, 4 high, 4 low, etc. OBII will not even read at the port.

Any other thoughts?

 

If I'm reading what you wrote correctly and you're saying the same behavior happened with a non-AGM battery, then I'd flip over the engine bay fuse block to look for corrosion and loose ends, then check both ends of the wire bundle that routes between the engine bay and cab block, detaching both to check for corrosion, including fully removing the connector and inspecting. We've seen previous cases where, for example, the fuse box was compromised. See 2nd pic here.

May be worth checking your cab fusebox also, test for continuity of circuits.

I mean, I'm hoping you didn't have an in-cab leak that's compromising your stuff, but ... if you're saying everything reads OK at the battery and alternator, and you're seeing weird shit in the cab, the chain of failure is pretty limited IMO. For the most part, cabling goes from the engine and its fuseblock, thru the cab wall, into the cabin fuseblock, then out to the misc interior components. I suppose it could be ECU fail, but I think you'd see more widespread problems than just cluster/gauges.

Another option, which I've never seen, is your gauge cluster is fuckered-up. But, like, literally never. seen that before. However, if things read OK with batt and charging, I don't see many other options there....

 

All great points I will check wiring going into the cab and related areas for corrosion.

I tested all interior fuses earlier as well I tested every fuse in my truck! I appreciate the help, this sucks.

 

No problem, keep us posted and good luck!!

If you find it's interior, you wouldn't be the first vehicle owner of any brand to have a lower-windshield leak caused by inevitable corrosion of the seal every car can see w/age. Unfortunately, most people don't realize they have the leak until something starts doing weird shit.

 

I found my issue. Basically, I got pissed so I turned on the truck and stuck the meter on the battery and started man handling all wires going to and fro the alternator and to the battery. Grabbed the wire from the battery to the under hood fuse box and voltage jumped. That was it. I guess in all my voltage drop tests that one was not scoped it. So I sanded the crap out off all the connections (though they were good I thought already) and tightened down. Solid 13.6 volts.

I guess morale of the story is check all wires multiple times. I thought I had, I was wrong. The key was hooking the meter up while running and jerking the wires around.

Thanks for the help.

 

Yeah, I wasn't just being redundant above about tugging on the cables, check the cables, etc. up above, especially the one from batt to fusebox. I figured if pulling on the cable didn't expose it, unmounting the box and flipping it over would've gotten you there

Honestly, it's probably a good idea to replace everything from alt-to-batt and batt-to-engine-fusebox every 10-15 years, proactively. Just so this crap doesn't come up. I'll probably do it after AGM and alt upgrade, somewhere down the road. Feels stupid to upgrade the alt after just replacing mine, but ...

 

Ha! Yes, I will likely do that. I definitely want to still look under the fuse box too - seemed fishy the way that popped up.

I took the AGM battery out for now. I do have an upgraded Sequoia alternator in there now, the only upside of this process, I was going to do that anyway. I will buy that ALT-S fuse jumper thing when they get back in stock - looks like they are out for now.

 

Well, I keep posting in hopes others learn from my issues.

So today took the truck to work for the "field" test. Worked fine. Ran out at lunch to get my diode for the AGM battery voltage "update" and parked the truck and came back, would not start at all. Of course, I went under the hood and tugged at the negative lead going from the battery to the alternator fuse, and it started but acted erratic the rest of the way home. So I tore apart my under hood fuse box (breaking multiple pieces of the plastic in the process) to replace the cable and the alt 140amp fuse.

This is what I found.... The fuse was not blown, but clearly fried some, and I believe this is where my intermittent contact was coming from...

 

Hmmm interesting. That’ll do it though

 

Great job tracking it down. Is that fuse from inside the fuse box, or an inline fuse?

 

That looks like the alternator fuse under the hood in the fuse box.

 

Its the one under the hood - 140amp alternator fuse. A pain to get out.

 

Yup. Not trying to be all "told you so!" but ...

You're not the first ... you won't be the last. That's why it's a really good thing you keep posting updates. This thread is going to help several people in the future!

 

Agreed! You were definitely on point, just hard to believe. Now i need someone to post a sticky on how to replace your whole fuse/relay box. I broke it up pretty good getting it out. New fuse and lead to battery will be here tonight and will be closing the patient up!

 

Best advice? There's links to a copy of the FSM for 05/06 floating around here somewhere. I'd probably hit a JY, see if you can find a 4.7 with similar cab configuration (AC vs DC vs RC) and pilfer the box, then cobble together whatever broke.

That's probably the worst I've seen, and I'm super curious to know what initially caused it, but like the Tootsie Roll Pop commercial ...