My car squeals when I have the air conditioner on.

How do i fix it

Our 2003 Echo had a very similar (if not the same) problem. Loud squealing sound that would only stop at high rpm's, but always returned when idling. Very annoying. At the time, I suspected the serpentine belt being too loose as others have suggested. But in the end it turned out to be a failed component (the water pump) whose bearings were going out that was attached to the serpentine belt. Our car was coming right up on a little over 100,000 miles at the time. If you're at a similar mileage point, I would suggest having your water pump looked at.

You just need to tighten the drive belt, its very easy to do yourself (3 bolts around the alternator must be loosened - then you stick a pry bar between the engine and alternator and pry it back while a friend/spouse tightens the bolt and you are done, noise will go away. If the belt is old, you might as well replace it since it only costs $10 - the procedure is exactly the same.

It may be the a/c clutch. When you first turn on the a/c the clutch fails to start up immediately and the belt squeals in protest.. After the clutch starts to turn the noise will probably stop. If that is what is happening, you are in for a rather expensive repair. Take it to an a/c specialists and have them check it out.

My Toyota Echo does this too, it may be because I put in Xeon light bulbs that draw much more power. Since when my headlights are on and I turn on the A/C I have the same sqeals. I found changing the EFI relay fuse fixes it. You can get this EFI relay fuse anyplace. I just bought it at ADVANCED for 13 dollars. It you buy from a Toyota dealer it may be $50.