When you turn on the air conditioner high pitch sound.

Power steering pump

look for a loose or broken vacuum hose connection , pcv valve fault

blower motor might be going out. worn out bearings.

make sure the belt is not loose, if the belt is OK, then your A/C pump is at fault

I know i have the same problem, and i also noticed than when i open the Hood the whistle just stops, so i figure out it must be some air cycling in or out osmewhere, I found out my air intake connected to throttle body was misplaced a weird gap was left open allowing air to whistle. u might wanna check there

Slipping serpentine belt. Spray it with belt conditioner.

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that may be the a/c belt slipping.

have the belt and tensioner checked out, the belt may be good just need tightened if it doesnt have an automatic tensioner.

or the tensioner may be bad, in this case have both the tensioner and belt replaced.

there is the odd chance that the a/c compressor is going bad and locking up.

any good mechanic can quickly tell you the problem in under 10 minutes

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

Sounds like a constricted IAC Idle air control valve passsage. Fairly simple to fix. Remove air filter trunking all the way to the throttle body to allow access. The IAC allows air passed the throttle when closed at idle. Just on the inside of the throttle body in front of the throttle flap there is an opening in the throttle wall. This is the air inlet to the IAC; there is an outlet similar on the other side of the throttle. Use carb cleaner and cloth to shift the grime from this tubing and get it like new. Hold the throttle flap open to get at both ends of the IAC tubing. The IAC can be detached and cleaned to a shine. Reinstall the IAC and replace all air pipe ducting. Leave for about 20 minutes to allow any cleaner residue to dry out. When you restart you might experience a bit of uneven running but this will disappear very quickly as the last of the cleaner dries out

So when you turn off the air con the noise stops ..
If yes then its the bearings in the Air Con pump which is driven by the same belt and when turning the r13 coolant around the bearings being dry and worn out will start to make the noise Same as the water pump does when it goes, but yours is Air Con Pump.
DONT TAKE IT OFF YOUR SELF. RON

There may be a small hole or cut in a vacum line or possibly just loose. Also make sure the air filter box and the big hose to it are secure and clamps etc are tight. Pulleys and belts can make a high pitch sound also.