Why does my air conditioner make a hissing sound?
Why does my air conditioner make a hissing sound? I'd really like to avoid a trip to the mechanic. The hissing sound is most likely the refrigerant going through the expansion valve. It's how the AC works. The expansion valve allows the cooled and liquified refrigerant to expand, becoming really cold, which then flows through the evaporator. Why is my car hissing under the hood? If the hissing is coming from there, quickly and lightly press on the valve to help it seat. This is a common issue especially on older vehicles when debris gets caught in the valve. Check...