Power surging, Alt putting out 18 volts.

Hey everybody, stoked to be here with you all as I’ve been driving my Tundra for the last couple of weeks, it’s a pure work truck, I’ll post pics soon haha!

Anyway I am curious if anybody can diagnosis this problem; the battery gauge reads near the top and the power and all electronics will surge(ie lights pulsate) actually every electronic pulsates/flares? But all works fine..so far.
The altnator was shown to be putting out 18 volts and seems to be charging the battery fine as I have been driving/working with it the last few days.
I am inclined to think this is this my voltage regulator causing the alt to put out too many volts and the pulsateing of the power? Any troubleshooting suggestions? Any good DIYs?
My daily is a e36 and I am spoiled by all the good info out there on them, hoping to find some answers/ insight on tundras from you all.

Cheers and thank you for your time!

2002 V8 Toyota Tundra Access Cab SR5 Pickup 4D 6 1/2 ft

 

check the resistance from the alt-s fuse in the fuse block to the S terminal on the alternator if you fear something more than an alt. but this sounds like a failed voltage regulator.

if you had high resistance at the alt-s fuse, then it could be seeing a lower voltage at the alt, then the regulator will kick its voltage up to make up for it.. but this is a very rare issue. typically with the issue you have, its just a new alternator to fix.

 

damn. how the hell did i forget about the battery. LOL im just use to those showing up as slow cranking or not cranking at all. good call

 

Report back!

 

Just curious, how would a bad cell in a battery cause HIGH voltage when the truck is running? The voltage supply when running is the alternator. Unless the regulator sees a low voltage from the battery and causes an increase in alternator output?

Not doubting you, just trying to understand this.

BTW, Welcome to the OP!

 

Battery is good was just replaced, I’ll check the fuse as empty_lord suggested but it seems that most likely it is the voltage regulator based on all your responses and fact that is charging plus putting out higher than normal (18volts).
Any good DIY on voltregulater Is it a hard job??
Thanks I’ll report back.

 

Buy a New ($500+) or Reman’d Denso ($220ish) from Toyota Parts Programme. I just installed a Reman’d when doing my timing belt at 171k miles. The Brushes on the Original were worn past the warning nubs and out of Spec on measured length.

 

x2 I experienced a dead battery cell, but the surge to 18+ volts was only during the first couple minutes on startup.

 

My experience is that the regulator can only regulate to a particular max load. Once you exceed it, all bets are off for the regulator.

 

To replace the regulator, it’s built into the alt. You can technically replace it. But for warranty reasons it’s just best to order a denso reman alternator

 

Have you checked the output AT the battery with a known good multi-meter, or are you relying on the dash mounted volt meter? The one in the dash will be hard to get a precise reading from.

 

Can you elaborate on this? All bets off meaning that after that load is exceeded regulator is broke??

 

Yes I have checked at the battery with a good multi meter! Thanks.

 

Okay I’ll look in to doing this job, thanks for the info.

 

Okay gotcha so either way would have to take the alternator out, so looks like I’ll be replacing the alt..
I’ll report back still gotta check that fuse thing that you mentioned.
Thanks for your time.

 

$130 after core credit

https://www.rockauto.com/en/moreinf...3/m9EVjil84KnkDPE0AEZSEAFoibqATo6A74iAZa3ETyz

 

Meaning it won’t regulate. Not knowing the details of the regulator design, it’s difficult to say how it would react. My best guess is that the 18+ volts is the unregulated output of the alternator but I can’t say that with certainty.

 

So I was doing some more trouble shooting after driving the truck to pickup firewood and the battery light began occasionally flickering usually when giving it gas.
I was double checking the battery on the volt meter and it was reading between 14-17 cycling quickly through those volts. Although only if idling in park/neutral, in drive/ reverse the battery measured a stable 14.4-9 but just when idling.
Seems to be narrowed down to voltage regulator or possible circuit problem. Like you all said...but I had to be sure before I do any work.
Is it possible to just switch out the voltage regulator?
The truck only has 90k miles on it but is pretty beat up..

 

You can’t measure the battery if it’s hooked up and the truck is running

 

Dan's comment above still holds true...."You can technically replace it" and given you said pretty beat up, the denso reman alternator is still the best choice....IMHO !

 

I dismantled my Alternator for Post-Mortem. Based on that experience and seeing how gnarly things were in there, I’d stick with a Reman’d Denso per post #9.

 

Thanks all, Denso remanufactured is on it’s way to me, I will report back when the job is done.

 

Just finished swapping the alternator with a remanded Denso and that problem is fixed!!!
Took me 2 hours, dident even have to lift the truck tho it would have been easier. In some online DIYs I found they said to loosen the water pump but it was not necessary IMO.
Minimal tools; breaker bar, 14 mil socket, 10 mil wrench... totally worth it since the shop wanted about $600-800 for the job.

 

Strangely enough the top bolt for the alternator was a double threaded piece of metal with a nut and when I went to put it back on the I couldn’t get the deeper end to thread as the nut broke free so it is sticking out only a few centimeters away from the serpentine bent/tensioner...I’ll look for a replacement bolt/ the part if I can find the correct one..
Any body know this piece?

 

Gates Heavy Duty Belt (Green).

 

Haha that was supposed to say bolt not belt...
The upper mounting bracket for the alternator was a double sided threaded metal rod with a 14mil nut on it, but was very rusted so when I un screwed it the whole thing came out.
I think it’s the same length as the lower mounting bolt, gonna try pick and pull or just get a alternator bolt kit...