I have an 01 Subaru Outback and when I turn on the Air Conditioning, a strange humming noise comes out from the dash board consoll. It sounds like a horn with a steady tone and comes from behind the radio inside the cockpit - not from the engine/compressor area. The cool air go's away when this happens. The system is fully charged and my mechanic says the rest of the system is working. This problem comes and gos. It is driving me nuts and with the hot weather now I am suffering.
Can you help diagnose this for me?
Year: 2001Make: SubaruMake (other): outbackEngine: 4 cylinder
Just asking around, looking on blogs. seems to be kinda rare. Don't want to pay a mechanic to tear apart the dash unless they have a good idea of whats wrong. suspect its a valve or selunoide.
HI there! I have 2 ideas, first, drop the blower motor and make sure there is no debris in there. Sometimes leaves and such can get in there and cause quite a problem. This is fairly quick and easy to check.Second, it could be the H vavle in the a/c lines. It is located in the heater box right where the 2 lines come in and it is making adjustments all the time. It is what Subaru uses to make the freon turn from a gas to liquid.It may be sticking on you and making the freon make noise. This would also cause the cooling to stop. Take a hammer when it is doing this and tap lightly on it. You can see just a bit of it sticking through the firewwall where the lines come in. Hope this helps! Thanks
Have you ever replaced an H valve?
I will try tapping it like you suggest, but I wonder how labor intensive it could be to replace. I think you are right about it being a valve as it sounds very musical like a horn. Gas or liquid through a tight space would produce that sound I would think - or vibration.
It's definately not debris in the blower as I have experienced that many times - plus the heater runs quitely (except on defrost when the a/c blends in).
It is a pretty big job, about 8 hours. The heater box doesn't have to come all of the way out,but close. Maybe 6 hours to do the job. It comes out through the dash and not the firewall. That makes it a bummer.
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