2000 Tundra Intermittent charging

Calling all people who are smarter than me:


My tundra has a charging issue. It charges sometimes, and other times, it doesn't. There's no rhyme or reason to it. Tonight it stopped charging and left me stranded on the side of the road. had to get a boost and limp it home. The battery is fine, it has no trouble starting or holding a charge.


At this point my best guess is a battery cable, but I'm really at a loss. when I pulled into the driveway after getting boost the volt meter was pulsating up and down way lower than it should be (still not charging) before I shut it off. That could've been simply because it was dying and the engine was still idling though.


any ideas? how do I diagnose without simply throwing (expensive) parts at it?

 

Do you have a digital voltmeter? With the engine running, measure the voltage at the charging post of the alternator to ground. I know, it ain’t easy access, and you’ll have to pull the “skid” pan, and BE CAREFUL of the fan, belt... If it’s over 14V, measure from that post to the positive battery post. You should measure less than 0.5V, if more, you have an issue in that cable or the alternator fuse. Report back with readings, and I can elaborate.

 

alright, I'll give that a shot. unfortunately I won't be able to get at it until Wednesday night (school schedule). Thanks!

 

at this point best I can tell I'm getting battery voltage at the alternator. (12v or less if battery is dying) I assume this means bad alternator. anything else to try?

 

Drive up to auto store and have them hook into your computer for confirmation.

 

Did a TechStream Diagnostic and it gave me C1241 which is battery low positive voltage.

 

Check in the fuse box under the hood for a fuse labeled “ALT-S”, likely a 7.5A. (Not the main 100/120/140A Alt fuse)
I’m not even sure your 2000 has the ALT-S fuse as I couldn’t find a good fuse box diagram, but if it does, it’s a quick check. If all good, (or not there) I’d be pulling that alternator. Which then leaves the choice - do you bench test it, or do you just replace it?

On the chance that the issue is a sticking or worn brush causing the intermittant no-charge, bumping it the right (or wrong) way might just make it contact well enough to pass a bench test, but still not be OK long term. I’d probably just throw a Denso or other quality reman in it.

 

ordered

yep, I had already checked that fuse and it was A-ok. I bought a Denso reman on Amazon for $150.

Thanks for the help! I'll keep the thread updated when get the alternator and install it.

 

My 2 cents...
Skip the reman and get a new one. I've had 4 reman units on different vehicles fail within 6 months of replacement.

 

even from denso themselves?

 

Question: Did you fully charge the battery or replace it at the time of installing the alternator?

Just installing an alternator with a discharged battery is like giving it a death sentance.

 

Good to know!!!

 

Never used a Denso but according to the Amazon page it probably isn't done at the factory so quality depends on the one who did it

From the Amazon listing.
Note: Denso partners with other manufacturers to supply the parts your car was originally built with. This product is in a Denso package, however the part may have been manufactured by an independent Denso supplier.

Yup and they all failed the same way, no charge at idle but full voltage above 2k RPM. The last one failed when it was 5 degrees and I swore to never buy another.

 

Golden nugget.

 

I have to second Fester here. Every reman I have come across on Toyota's was junk. The last reman wouldn't charge at idle, causing all electronics to dim/slow.

 

welp, the order is placed. I appreciate the two cents. I hope mine is an exception.

 

Update: The alternator solved all my problems. truck is running well and charging with no issues.

Replacing the alternator s a bit of a PITA though. who on earth thought putting it underneath and behind the PS pump was a good idea?!

 

Did you end up going with an OEM alternator or something else?

 

Denso Reman from Amazon. $160 to my door.

 

Denso makes good products. Good pick.