Hello, I am the owner of a '04 Dodge Ram 1500, 5.7 Hemi, 65,000 miles. It has previously (1/29/07) been in the repair shop for power steering pump tube replacement (I think they either cut something or disconected something). Now, I need to use my A/C and I hear the automatice fan running, but the compressor will not engage. Also, when turning the heater speed on high it sounds like the air is being forced through the vents and creates a wihistling sound.
Take it back to the shop and complain.
If they did cut or damage a refrigerant line, then yes, the compressor will not work. There is a low pressure cutout to prevent damage. Look and or feel all the refrigerant lines and devices for damage. Even a small hole will produce oil at the leak.
As for the whistleing, I'm not sure what that would be. Does it only happen when you are on defrost? Then something might have fallen down the defroster. Does it happen only with the heater? There might be a leak in one of the air ducts. Try to pinpoint the location of the noise.
It could be some material inside the ducting somewhere.
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