What would cause a whistling from the heater?

Answer 1

My car was making a noise, although I would describe it as more of a "hissing" sound, from the heater/AC control panel. It turns out to be the heater control assembly that was bad. I was told another possibility when you hear that noise is the water control valve.

sounds like a system with vacuum controls( found in higher price/luxury vehicles ) for changing settings...def.,floor/heat,vent,etc. a cracked hose-or a hose that has popped off of the 'nipple' it fits on. does it change when you change 'mode-heat,def.,etc? also, there is a ' manifold ' where all the air tubes are joined and feed vacuum to move doors,etc. for heat-def. etc... somewhere under dash-passenger side-or near center that can leak at main vacuum feed. it looks like an cow's udder-clear plastic air lines connect there and go to respective controls for heat, def.,vent,etc. move the hoses a bit- with car runnuing-listen for change in volume of 'hissing'. of course-this problem could be at the control valve in the dash where you make the desired changes for heat,def., etc. the control valve is expensive- i have bought/sold vehicles for 40 years. i am a supporter of 'junk yards '...er,auto recycling businesses. they will pull the part-now you need to find an installer- this is a bit complicated,based on vehicle and location of hissing problem.finally...do all of the options for heat,def., etc. operate correctly-try runniong the system "thru the paces" a few times and listem for changes,location-as i said before-good luck...