Alternator voltage jumping around

Had my battery light on my dash flash on once yesterday so I switched my scangauge to voltage. Start my truck and it’s at mid 14s then get on the highway and it drops down to low 12s. Stays there for a few minutes then climbs back up to 14s.

guessing my alternator is going? Just wanna confirm before I spend the cash. Loose ground? Fuse? Currently sitting in traffic so I figured I’d ask before I’m home.

 

Falls down to mid twelve at idle. Can force it to climb with rpm in neutral

 

Dash light has not come back at once though.

 

Could be all the above Break out the Meter .

Open fuse most likely would cause a no charge condition

It does sound like a poor connection

How old is the battery ??It might be taking that long to recover after starting .

The light came on once now it is off or is lit all the time??

Once it climbs back to @ 14 VDC it stays there till you shut it off.

What kind of load on the Alternator Head lights Blower motor on High??

Figure out the problem before buying something you might not need.

 

It’s jumping up a down as I drive. Especially with rpm. I’ll check load once I am home.

 

Alternator takes like 3o minutes to remove by Helen Keller. Take it out and have it tested by Pep Boys

 

Not something as simple as a loose belt??

 

I would start simple. Clean the battery terminals. Check serpentine belt tension. Check and clean grounds. Also I would not drive farther from home than I had to; it may be the alternator.

 

Sounds like you got the right basic approach/plan to addressing this. First things, like you say, triple check grounds and connections.
Once engine is at operating temp, at idle how many volts do you see? And then also at operating temp, at 2000 rpm or freeway speeds, what voltage you seeing?
These OEM alternators, if yours is in fact original, are high quality units. The bearings rarely fail and the internal electrical are high quality. There is a strong chance that all you need are the brushes that wear down with age/use. These are meant to be replaced themselves, not replace the whole alternator. Much much cheaper, and you keep the high end oem unit, you don't end up with some parts store alternator remanned by some knucklehead.
I'd definitely encourage you to replace a couple of 'intended to be consumable' brushes on your OEM alternator. It's cheaper, and you get to keep the high quality OEM one.
Let us know what you figure out

 

Grounds are all good. Belt is healthy and tight (supercharger tensioner but def not slipping and tight as it should) holds 11.9 now after getting home 20mi. Doesn’t fluctuate much with rpm anymore.

gonna pull it and find a new one.

 

Most likely it's the brushes. It's a lot cheaper to just replace those, but if you want to spend the money then just get a new one, but remember a lot of aftermarket ones can be poor quality. Denso is probably a safe bet.

 

Get your alt. rebuilt if that's what it shows it needs,,, no aftermarket.

 

Also forgot to mention, if/when you go the replace the brushes route, they don't have to be Toyota OEM kinda thing. You can just grab em from the local auto electrical house in the area or online or a local stealership. Even a chance the parts stores have em, but I've never found them at the aftermarket parts stores like VatoZone, etc.
The point I'm trying to make is the brushes don't have to be OEM, you can use generic and not compromise reliability. Kinda like starter contacts, same scenario

 

Never rebuilt one but replaced to many to say. I must admit about a week ago we did some wheeling with some super silty water crossings and it’s likely I sloshed that disgusting soup into it as it was sprayed everywhere in my engine bay.

 

Replacing the brushes is a pretty easy job and you would be able to tell if they were bad once you took it apart.

 

If it were the brushes I would expect the voltage to stay down. If they're worn out, they're worn out. Its not like they move around much either. I think in your case I'd suspect a loose wire or a bad voltage regulator.

 

If he drove through salty water that got in the alternator like he said it could cause all sorts of problems. In that case it might be harder to test and find the problem. The brushes are still easy to check even if the plan is to replace the whole thing.

 

As I ran it more the voltage was slowly dropping in my driveway. It was down to high 10s by the end of my volt test and the battery light on.
It wasn’t salt water but the muddiest clay water you’ve ever see . This spot is notorious for killing alternators so new is likely just the fix.

 

Maybe if you included the muddy soup engine compartment bath from the get go ??

I would check the alternator plug they are good for corroding in the best of times.

 

gotta keep y’all on your feet as far as diagnosing. I didn’t dunk it so didn’t immediately assume. Just curious opinions. That’s why we post here right?