Intermittent Squeeling

[ex-x-fire]

Maybe starting it the first way has to do with the a/c compressor engaging while its trying to start. The 2nd way, maybe the a/c is already engaged.

[naossoan]

Originally Posted by ex-x-fire

Maybe starting it the first way has to do with the a/c compressor engaging while its trying to start. The 2nd way, maybe the a/c is already engaged.

I'm not sure what you're saying. It would squeal sometimes whether the AC is engaged or not.

Originally Posted by NYC-SE

The blower motor has nothing to do with it, it is not driven by the belt. The alternator, however, is. The reason the squealing stops when you turn off the blower motor is because now the alternator is under less of a load and therefore the belt is less likely to slip and squeal.

Are you saying the alternator is bad, or the belt is bad? Or both? I should mention that the guy I previously mentioned claims he replaced the accessory belt and it was still squeal.

https://www.youtube.com/watch?v=HRrVMtyIqIY

I find it interesting the video is called "mystery solved" when he didn't actually solve anything. He just discovered it wouldn't squeal if he started it slowly lol. But it's exactly what's happening to me....

https://www.youtube.com/watch?v=6a0IeIE4qR4

[NYC-SE]

Originally Posted by naossoan

Are you saying the alternator is bad, or the belt is bad? Or both? I should mention that the guy I previously mentioned claims he replaced the accessory belt and it was still squeal.

No I doubt it is a problem with the alternator. More likely the belt is loose or worn. How old is the belt?

Or perhaps nothing is wrong at all. The squealing related to the speed of turning the key thing is real. Numerous people here have reported the same thing. I can even make it happen with my car as well and my belt is fine.

The guy in the video posits a computer - alternator communication issue as the cause. Perhaps he is right. I'm not sure of the reason but whatever it is the phenomenon is real.

[B.B._07]

It's been discussed here many many times, the solution to your problem is the belt needs to be tighten end of story. The Yaris does not have a auto tensioner for serpentine belt like the vast majority of modern cars do, so even a new belt will stretch after some time and the squeaking can come back. Mark the position on the tensioning bracket, and tighten in small increments until the noise is gone and you're done. Weather or not the increased alternator load theory is right or not is not relevant, it's making noise because there's not enough tension to keep the belt from slipping.

If you need some guy on Youtube to show you how, here you go:

https://www.youtube.com/watch?v=QMkNQULvH4I