Whining sounds once engine is running and even when the AC is off!

The air conditioner compressor is driven by the engine. The compressor itself has a pully on it that is mounted to an electric clutch, When the Air condition is no on, the pulley still rotates on the shaft but the clutch is not engaged so the compressor does not turn. If the whole assembly is starting to wear then the bearings in the pulley will whine. Due to the the heat that builds up from this, the dealer or service tech will replace the whole compressor and the clutch, You are looking at a cost of near 2 thousand dollars.

Check the idler pulleys on all the engine belts, esspecially the AC compressor. Could also be a worn or frayed belt.

does yours have a turbo fitted as it can be this. if it dont go up or down with engine speed it can be somthing ells , like a wheel bearing catching brake shield ( onto the disc) or even the thrust bearing on the clutch. auto dont have this.

would need head under the bonnet to know for sure but feel the AC lines as a lack of gas can cause a noise like this but its not often that you can hear it above the clanking of the diesel engine ,no petrol ones here at our fuel prices

Without knowing where the sound is coming from, theres no way to know if it is important.
Is it possible the noise is the ac clutch, and the ac compressor is locking up and killing the engine ?

did you get a service bulletin on the clutch replacement on the ac it could be the problem you can call the dealer with your vin number and they will tell you if there is a recall or not do some tests like put on the ac while the car is running and see if the sound changes and shut it out to see if it changes you also could have a bearing in the tensioner or just the belt is to dry so there are a few things to check as for the brakes prob it might be possible that they are dew to be done

You may be having AC problems but that is not what happened when the Steering locked unless the AC is on the same belt as the Power steering unit. That whining you are hearing when you turn is actually the power steering unit being low on fluid or the power steering pump going out. Based on what you have described my guess is that the unit has gone out and needs to be replaced. As far as the AC compressor is concerned, if the unit is low on Freon it will not engage once it gets too low unless the clutch goes out. When you look at the center of the AC compressor when the engine is running and the AC is off you should see the pulley free spinning and the very center of the pulley won't be spinning, that is the clutch Dis-engaged. When you turn the AC on the Clutch should engage and allow the compressor to work. You will hear it kick in and kick out repeatedly if it is low on Freon. If it is too low it will never kick in because the low pressure switch won't allow it.

Oil dipstick has nothing to do with whining noise

Check the power steering fluid if its low it could cause this. Also could be alternator, water pump, ac compressor, or idler pulley. My bet would be on the idler pulley, its the one that keeps the belt tension constant. Remove the belt and check this pulley for slack also spin it by hand.
Good luck, dont forget to rate.

The A/C compressor constantly turns because the pulley is connected into the serpentine system. The whining noise is pretty indicative of a low charge in the A/C system. I would start by having your A/C pressure checked and charged if needed.