i replaced my AC coil,heater core and blower motor this past week. i noticed that when the AC is on and when the defrost is on i get a whirring noise at low idle(like sitting at a light or stop sign).the second i hit the gas,in idle or in gear it goes away. it almost sounds like the blower wheel is rubbing but it does not do it with the fan/vent on only. it was cooler tonight and i noticed that when the compressor would cycle it would only whirr while the AC was on. i'm not sure if it's an airflow issue with the blend door or what? could be the refrigerant i guess.
i replaced the hose(with orifice),accumulator,compressor,evap coil and while i was down there i replaced the blower and heater core. i do hvac for a living so i'm not a complete dummy when it comes to hvac stuff. it's just hvac car stuff. i did a triple evac with my third evac on a vaccum for over an hour. any input would be helpful. thanks,
PS it also does this at every speed. 1-4/low-high