Belt Squeal on my miata

[atlnb]

I've been dealing with this for quite some years now. When driving at night or with my headlights on, my car will have this terrible belt squeal. Sometimes it goes away while I'm driving, other times I have to either turn my lights off or turn my car off to stop the squeaking just so I can drive until the next time I stop and the belt starts to squeak again. I've had the belts tighten more times than I can count and have switched to smaller belts to keep the make sure there is enough tension but nothing seems to stop this belt squeal. This only happens when my lights are on. During the day, not a single problem, car drives like nothing is wrong. Is it possible I have a bad alternator and need to switch? when the car squeals, I notice the cabin lights dim a good amount as well. Any input would be greatly appreciated.

[BoBo]

I had that same issue when I installed a new belt. It's just that I didn't tighten it enough and let it squeal for many months. Finally I was off of school, so I re-tightened it and the squeal is gone. Your belt could be to long, in other words, not original. I'm pretty sure if you tighten it enough that it would go away.

[jux]

Too much draw on the alternator? Maybe bad bearings or the whole thing is on its way out.
Never had this issue personally. Only noisy belt I had was due to glazing.

[ibid]

In our case when this happened to us, it turned the bracket was cracked and breaking away... on our former 1.8 95 that is...

[atlnb]

I don't think it's loose. I changed to a smaller belt and had that tightened and I'm still hearing this squeal. I am leaning toward the bearing being bad or the entire alternator is gone. I just went ahead and purchased a used unit from Planet Miata to see if that changes anything. It's only $50 so hopefully it's a cheap fix.

[jux]

Let us know if the replacement does the trick.

[atlnb]

so it's been a month or two since i've changed the alternator and all the tensioners. this seemed to fix the problem. i would have done piece by piece but I couldn't take it anymore. i actually had the belt break while driving so i am assuming the tensioner was the real problem

[— kung fu jesus —]

Have your alternator and battery tested. Also, test the battery voltage at the battery poles with the lights on versus lights off, car running. Off, with the car running, should be 14.1v IIRC.

[atlnb]

Thanks, I'll be sure to check that out

[— kung fu jesus —]

Just an observation, but the NB alternators/charging system doesn't seem as robust as the NA. In racing, they seem to be more of an issue or annoyance. I know the two chassis are different in that regard, but I am not well-versed in electronics and generator design.