Light hiss from passenger side interior when A/C is running

[scott916]

I have a 2000 Accord with roughly 150k miles on it, and when I turn on the A/C to defrost my windows, I get a light hiss from the passenger side footwell. It stops as soon as I disengage the A/C switch, but operation seems normal. Is this a sign that the compressor or any other part of the system has a leak?

 

[cardiac]

Probably not the compressor, but a vacuum leak. They can be tough to track down though.....

 

[Pacfanweb]

Vacuum leak from one of the actuators. The tube connector might have just come off the actuator. Drop your glove box down and look in there...see if there are any small metal canister-type things with a nipple coming off of it. If there's no vacuum line attached, it's probably nearby.

 

[thomsbrain]

I wouldn't call it a hiss like air hissing, but the A/C in my 91 Accord always made a faint sound like water running through pipes from the passenger footwell when you ran the A/C.

 

[boomerang]

This may be a normal sound. When the refrigerant enters the Evaporator in the interior of the car, it passes through an orifice tube. At this point the refrigerant becomes super cold.

It enters the tube at high pressure, and as the pressure is released, the cold refrigerant floods the evaporator, warm air in the car is blown over it and the heat transfers to the refrigerant. At the same time, moisture is removed from the air.

Think of releasing high pressure through a small opening. A hissing sound would be normal.

If this is a sound different from what you normally hear, something has changed. Is this a sound you've not heard prior?

 

[Rubycon]

Originally posted by: thomsbrain
I wouldn't call it a hiss like air hissing, but the A/C in my 91 Accord always made a faint sound like water running through pipes from the passenger footwell when you ran the A/C.

Sounds like bubbles in the liquid line which runs up to the expansion valve right before the evaporator.

Originally posted by: boomerang
This may be a normal sound. When the refrigerant enters the Evaporator in the interior of the car, it passes through an orifice tube. At this point the refrigerant becomes super cold.

It enters the tube at high pressure, and as the pressure is released, the cold refrigerant floods the evaporator, warm air in the car is blown over it and the heat transfers to the refrigerant. At the same time, moisture is removed from the air.

Think of releasing high pressure through a small opening. A hissing sound would be normal.

If this is a sound different from what you normally hear, something has changed. Is this a sound you've not heard prior?

Yes definitely sounds like expansion valve hiss.

 

[Nessism]

Yup, expansion valve hiss. Normal. Drink a beer and relax.

 

[scott916]

I never noticed it before, although it is very quiet and wouldn't be hard to miss. If it's nothing to worry about, I'm not going to bother paying for taking it in and having it looked at. Thanks, everyone.