My a/c pulley or clutch is making a screechy noise it only makes the noise when a/c is off when i turn the a/c on the noise stops. i took my car to a shop and they tightened something on the a/c. What can i do to stop the screechy noise it's probably simple. Oh by the way it's on a 2.3l Quad 4 engine (achieva)

Your serpentine belts tension is loose or the belt is going hard. Check the tension on the tensioner pulley and condition of belt.
The belt is slipping on your accessory pulleys when a load is placed on them such as power steering, alternator and clutch fan.

With belt off spin pulleys and feel for slop. Bearing going bad?

the clutch and bearing assembly is failing it is a freewheeling pulley till clutch is engaged but it has bearings which can fail

Problem could be either the fan clutch or the water pump, neither part should have any play in it. If the noise is like a jet engine, it is likely the fan clutch.

yes! you should be able to turn the clutch by hand.run the car,open the hood,have someone turn the a/c on.you should see and hear the clutch engage.

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A failing AC compressor clutch will make noise more like a rattle but it will become hot enough when it is failing that the rubber grommets around the clutch plate will begin to "stink" as they begin to melt and fall out. It will smell like burnt rubber smoke.

If you remove the drive belt you can try to see if there is play in the pulley for the AC compressor but you won't be able to "engage" the clutch to test it (uses electrical switching). If you can spin the pulley and it makes noise, suspect a failing compressor clutch.

While you have the drive belt off spin the water pump pulley and you should only hear a gurgling noise from water in the motor being pushed and no metal on metal noise whatsoever. If you hear a clunking noise when the motor runs you could also have a worn motor mount so you would want to check those also.

Sounds like the serpentine belt is slipping and perhaps struggling to turn pullies.. this would result in horrid squealling noises especially in cold damp weather and loss of power steering ability when A/C is on

(A/C on equals extra strain on the belts grip, when turned off the A/C pulley spins freely hence less strain)

Check out he clutch fan.

When you have the belt off, spin that idler pulley and see if it turns easily or makes noise. Check if the bearing feels good and smooth or if it wobbles any. While you are at it, check the fan and fan clutch to see if they turn smoothly also. There should be some resistance to the fan clutch, and make sure the fan isn't rubbing on anything.

Replacing the idler pulley is usually done as a unit since the bearing is part of the pulley.

Does this noise occur as the engine is cranking over to start, and as it just start up? It's probably the belt slipping on the pulleys. If the belt is original, or showing any cracks and splits, replace it. Keep the starter. countrycurt0