2006 Prerunner Voltage issue

As some may have read I replaced an alternator that I THOUGHT was going bad. I had the diode howl and voltage started going down. I have a USB charging module installed that gives me real time voltage and while idling it would drop to 11.7 or there abouts, and no more that 13volts (14.2 was the norm) on the rev on the interstate. I replaced the alternator (130 ac delco from Autozone), jacked up the belt alignment which then jacked up my harmonic engine seal. $150 later (for the seal) I am still getting the low voltages. And this morning after the truck had sat since Friday night, I have to jump it off.

I've been getting low voltage at idle 11.7 and 13.8 at rev on the road. Evidently it wasn't the alternator? I see that the voltage regulator is built into the alternator. I have bad luck, but it can't be THAT bad.

Is there another issue I missed?

Please don't start with the "ac delco sucks" thing either. It is what it is. I'm going by Autozone on the way from work this eve to check and see if it is the alternator.

 

I don’t know what to tell you for the alt, but a good way to gain more voltage is to do the big 3 upgrade. Not that hard of a mod (upgrading your stock grounding wires) just look up a tutorial on yt.

 

As I sit in the truck writing this the voltage is at 11.5.

 

It would be nice if it was that simple more investigation to follow.

 

Just sitting here idling the truck and revving it killed my voltage down to 11 .6. I'm going to have to jump it to start it later today. This is never been an issue I've had the truck for over a year and it's sad for as much as a week and started no problem.

 

Have your battery load tested. I just had my son's battery develop a bad cell which dragged the voltage down similar to what you are seeing.

 

Ya going at lunch, AFTER I jump the bastige off!!!! ugh!
Alternator diode howl
engine seal (ya my fault)
now the battery! Ugh.

 

Unless you got a Toyota rebuild kit, bought a New Toyota or who makes it, or a Toyota rebuilt. Most of the box store alternators are crap for our trucks

 

Yeah they are i had to replace an alternator in a scion xa twice in one week

 

Bought another alternator, will have to put it in this evening. They will refund me the $$ on this one when I return it. Just gotta watch the belt this time.

sucked all of the juice out of my battery on the way to the mechanic, he checked the voltage once shut off and the battery started regain voltage. Started it back up and removed the negative terminal, shut right down. It throws a charge at high rev, put the A/C on and it immediately begins to go down.

Pretty sure it's a bum alternator.

 

Installing larger ground wires isn't going to increase the voltage in any way shape or form.

Ohms Law: https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/voltage-current-resistance-relate/

 

I would definitely recommend this along with making sure to clean and tightened the battery terminals. A faulty battery can simulate the same issues you are experiencing especially if the 2nd alternator replacement doesn't fix it. I would also recommend carefully inspect the wiring from alternator-fuse box- battery.

 

Would it make a difference if you have lots of power running off the battery? Like large sound systems and subs?

 

It may give you a better ground, but it is not going to increase voltage.

 

It won't make the alternator output voltage higher, but it will decrease the voltage drop, so more of it gets to everything else. Not that it would fix OP's bum reman alternator, nor would it (well, hopefully not, anyway...) remedy a voltage as low as he was seeing. If the cables were dropping it that much, wow...

I did it on my 1st gen years ago, and couldn't believe how much difference some 2ga and crimped & soldered lugs made. I had been a doubter on it myself but figured I'd try it (I think just for giggles, not to try to fix any particular issue) and it did in fact raise the unloaded voltage readings at the battery (while running) and starter terminal, by a good bit.

 

If you have that much of a voltage drop then the factory wires were not seated correctly. It had nothing to do with the "upgraded wires".

But to each his own...

 

I would have checked the voltage with a high quality DVOM, since your USB voltage display could be inaccurate.

 

Thanks for all of the input this has been educational.

I got the new alternator, and I was going to put it in that evening. After the first thunderclap directly over my head that evening I called it a night! I put the battery on charge overnight and had a fully 12.8 VDC in the morning. It is charging and voltage levels are being maintained now. Never goes below 12VDC when idling and we are back to "normal" levels ie, 13.8 and 14 VDC while driving. A/C etc does not drag it down more than a 1/10th of a point.
I'm going to have the batter checked to confirm that it is good. It's a 2017 so I'm hoping it is.

Speculation is welcome at this point. My mechanic of 25+ years said that it's "possible" that the battery was so low from the previous alternator that it could not recoup. I'm used to the concept that the alternator will charge the battery, not "maintain". But with that said I had not driven it any significant distance to give it the opportunity to actually charge. Regarding the cheap USB Voltage info, I agree and only use it as a yard stick for changes. And with that said it has been on track with the other voltage meters used by myself and the mechanic.

Now I have a new alternator in the back seat and debating if I should change it out for the other one. My biggest fear is dinking up the fan belt again and having to fix another seal. Gack!!!

 

The possibility is high that the battery being discharged too much for the alternator to bring it back up. Esp since it seems to be working after a proper charge. You may have shortened the life of the battery, hard to tell.

 

No 60v Milwaukee battery to jumpstart the battery... Noted.