Hear a higher pitch whine and AC wont shut off. on 2004 Chevrolet Express 2500

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I hear a higher pitch whine coming from engine compartment.Only when in gear and get louder as i increase revs. Also the A/C comes out so cole it put frost on the window and this was while it was on vent only, A/C wasnt even on. Check engine light has been coming on/off intermittently.
(1) Answer
Sorry I cannot help you with your A/C issue - I have never hear of anything like you are describing. fault code(s) were set in the powertrain control module when the check engine light was on and will need to be read with a code reader or scan tool. The stored code(s) will indicate a part or system failure which will need to be checked out. You may need a qualified technician to listen to the noise from your engine in order to determine the cause.