I have no idea what could be causing this... it's been happening for years, but I've never thought anything about it until tonight when I was out driving around. Any thoughts?

 

When you say WOT, do you mean high rpm? Weak springs in the brushes will cause them to bounce at high rpm. I just went through this with a rebuilt alternator, a brand-new one fixed it. If it happens at WOT and is independent of rpm, I don't have a clue.

 

I've been having the same issue since my original alt went out about a yr ago. I've been through several remans and a few used ones. Still having drops to 11v at wot. Usually above 5600rpms on the bottle.

 

Yeah, it would be high RPM, the only time I get the revs high enough to do it is WOT, that's why I said WOT

 

In my case with bigger injectors, there is a table in the tune that adjusts injection according to voltage. This table had all stock data, most people don't know it needs changing with new injectors. So when my voltage dropped at 5000 rpm, the AFR went lean. Not a good time for that to happen.
In your case, it is just a warning telling you to plan on replacing it. I imagine it will progressively happen at lower and lower rpm.

 

Belt slip. Check the tensioner or the belt. If the belt slips on the crank pulley everything is slowed down.

 

Its not belt slip!!!!!!!!!!!!

 

Could be slipping on the crank?

 

GET A NEW ALTERNATOR! Its dieing on you, I had this problem couple months ago, and I love to rev the higher rpms. Its sending less power to the coil packs and killing your performance. It took about a full 3 weeks for my batt light to actually come ON, then I really investigated. Changed the alternator, now ALL my HP is back. I couldnt even tell I was loosing it.

 

Nope...it has something to do with the rectifier in the back of the alternator. Once the diodes start going out its all down hill from there. All the reman units use cheaper rectifiers that are rated at a lower amp and get hot and start failing. Once they cool off they charge fine and test fine. The original units that come on factory cars/trucks are the best to get. They have a better higher amp rectifier on them.. Supposedly 50 amps vs 30 amp cheap parts. Even the reman from GM have garbage parts. Only fix is usually another alt from a yard that is a OEM pull off...