What's going bad in my alternator? (It's whining! )

Soo about 2 weeks ago was out dirtbiking, got in my truck to go home and there was a whine from the engine bay, no lights on the dash nothing.

Figured idler pulleys.

Got home popped the hood and got a wooden dowl and to my surprise it was 100% the alternator in some way. While I was listening to it, the whine (a light hum) went away.

Went ok.. I'll see if it comes back. Well today it came back.

So while running I popped the hood and unplugged the green plug with 4 wires the at back of the alternator (presumably the voltage regulator control? ) And the noise goes away instantly, and instantly comes back when it's plugged back in.

Should I pop the brushes out n clean em up? Or could it be the whole diode assembly? The alt spins smooth.

This is on a 2013 v6 TRD OR with tow package with 106k miles. The alt itself looks almost new, truck has never seen mud.

 

Alternators have 3 separate phases. When you have a failed diode in 1 of the phases, it goes charge, charge, no charge, charge, charge, no charge... this causes the whine you hear. Also it will only have 2/3 the amount of current output. By the time a diode fails, the bearings and brushes are in the 11th hour. Replace the alternator.

 

Daaaaamnit! That makes perfect sense.

Whelp, which one should I go with then? Denso new or denso reman?

 

I can't help you there. Search the forum for Denso alternator and see what kind of experiences people have. All I remember reading is that Denso is the way to go.

 

I let mine whine just a little too long on my old truck, it caught fire from the bearing going bad.


These were the ball bearings

 

If you can shoot for brand new I would go that way bro.

 

Personally when I need a new “moving” part like an alternator I always go with new. An alternator works hard, it rotates millions of times before you need to replace it. I just don’t want to mess around with a rebuilt. Yes a new can fail but I think less likely.

 

This just started with mine (its true that letting a vehicle sit is the worst thing for it!) - really strange wimpy noise sound from under the hood which stays in harmony with the engine speed (and not in a good way either). Hoping that alternator is easy to remove and replace.

 

Super easy quick test was unplugging the 4 pin connector you can easily get to it.

 

Reman Denso is fine.. they're one of the companies that actually put a little effort into theirs

 

I have installed 2 re-manned denso units now and they both have been solid after 75k miles. I would go this route

 

Honestly cant for the life of me find a NEW denso unit, everything is remand.

LOL shoulda refreshed the page.

 

Geez Muddinfun what is up with giving a short clear concise simple answer? I mean nobody else seems to do that, why are you so special! lol! (also total sarcasm in case it wasn't clear - great answer!)

 

Ive had fantastic success with a local shop that will rebuild your unit. One on a 300zx-t, which required a sway bar drop to access, they rebuilt, including the R&R, for less than the retail cost of a reman from any parts house around here, with an equivalent warranty.

Something to consider if there is one in your area

 

There is and its something I have considered. But turn around time is the probs, need the truck this weekend

 

I trust Denso above the majority of parts ACDelco being the second.

OE is always my first go to if it's just as affordable which sometimes, it actually is.

I really do my absolute best to stay away from any other companies at this juncture because it seems as if they are all owned by the same cheap Chinese douchebags.

 

LOL Let's just say I've taken a lot of broken shit apart to see what's inside.

 

yeah just pulled the alternator (napa has a denso reman on hold for me).

Brushes and slip rings have TONNNNS of life left, bearings smooth as can be. But one of the diodes is definitely seen better days *sad face*. @Muddinfun you were spot on with your diagnosis!

 

LOL. Thanks.

 

He's a man of few words, but he knows what he's doing.