Auto Air Conditioning & Heater Repair: air conditioner, drive belt tensioner, power steering pump

Question
1998 astro van,170,000 km.v6
when air conditioner is switched on to cool it works great,BUT the noise that it makes like awwwwrrrr sound . turn off the air no noise , turn to heat no noise ,turn to defrost the noise starts again. My check engine light is on steady had garage checked the computer system ,it checked out ok. what should I do next,need help in Canada. THANKS JOE

Answer
Hello Joe ,Sounds like a/c compressor vibration when it`s on.You might need to replace the compressor with that high mileage.Before you do that,check the power steering pump support/ mount brackets.They have had a problem cracking and makes the that noise when they a/c comes on.The a/c compressor causes some vibration when on,but if that bracket is cracked it makes more noise. Also check the drive belt tensioner, if the spring is weak the a/c compressor creates drag and the  drive belt can flap while the engine is running.

Good luck, Davidt