AC hissing noise

[bull5]

Hi
When AC is working I hear an hissing noise coming from the passenger side. It comes every 20 seconds, I think when the compressor is on. AC is working so far.

Any suggestion?

[4speedfunk]

Crank the stereo.

[adventuredad]

I think I have about the same sound. Every once in awhile it’s a hiss from around the glovebox. Don’t always hear it and certainly haven’t had the AC on, all heat right now.


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[adventuredad]

Have you come across any more info on this? We’re getting into warmer weather and I’m noticing it more often. I don’t have the ac turned on but still getting the hiss u set the glovebox. I did need to run ac recently and noticed I had to have it set as cold as it would go to get it to cool down. Seems a little off and I’m expecting I’m gonna have to troubleshoot it as we get into warmer weather.


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[Jeepwalker]

Is the A/C system working (cooling) properly? Does it sound like pressure equalizing itself? Such as when a person turns off the car and the pressure in the A/C system equalizes out?

[adventuredad]

Is the A/C system working (cooling) properly? Does it sound like pressure equalizing itself? Such as when a person turns off the car and the pressure in the A/C system equalizes out?

Mine is doing it with the AC OFF, haven't been running AC yet this year, that's the strange thing to me. I will try and check with the AC ON and see if there is any difference. The only time I ran the AC was a couple weeks ago and it seemed the only time it would actually cool was with it set on the coolest setting, seemed strange to me. Also when I am using the heat, it puts out extremely hot air- hotter than any other car I've driven. Is this typical? I know the I5's seem to run hot and heat up quick but does it affect our cabin heat that much?

[Jeepwalker]

The ac compressor should come on with the defrost too. In case you might have been using it.

[adventuredad]

BINGO! Didn't even dawn on me, yes I run the defrost quite a bit with the humidity during the rainy months up here. That explains the hiss for me, I'm guessing it's just louder in the H3 than it has been in previous cars. Thank you for that!

[Jeepwalker]

Great!
Nice when problems turn out not to be problems after all!

Cheers..

[bull5]

Can be a bad AC expansion valve? I have installed a non original one (4 season). Thanks for your help.

[Clark]

maybe Check the fan blower. mine makes a hiss sound and a light whistle noise on low. Goes away on high and when I turn off the blower.

[bull5]

maybe Check the fan blower. mine makes a hiss sound and a light whistle noise on low. Goes away on high and when I turn off the blower.

Hi
If you turn off the blower the AC system is automatically cutted out as I know.

[JPaul]

You're going to hear the hiss of the AC when using it, it's the valve opening to let more refrigerant into the evaporator. The higher the temperature difference (ambient air temperature) and the faster the blower is going the more often the valve will open. When the valve opens you'll hear a hissing sound and once the pressure equalizes enough the valve closes again. As the air going through the evaporator cools off the pressure on the evaporator side of the valve will change enough to allow the valve to open again to let more refrigerant in. This is perfectly normal as far as I am aware.

If you're concerned about it then the first thing to do is check the temperature of the air coming out of the vents with the AC on full blast on a moderate day (70 degrees Fahrenheit or about 21C). If I recall correctly it should be around 45F degrees or so (~7C to 8C). If it's much warmer than that then there is some issue, either the charge of refrigerant is too low or too high, or several other reasons.

Another thing to check is the charge level of the refrigerant. You'll either need a dual gauge set specifically meant for AC, or just take it to a shop to have them check the levels. You need to check both the high and low pressure sides to know if the charge level is correct.

But if it feels like the AC is blowing cold air properly then it's probably fine, it doesn't take much for the AC to stop cooling air enough to be noticeable if something is wrong with the system. We just have a noisy AC in the H3's.

[bull5]

You're going to hear the hiss of the AC when using it, it's the valve opening to let more refrigerant into the evaporator. The higher the temperature difference (ambient air temperature) and the faster the blower is going the more often the valve will open. When the valve opens you'll hear a hissing sound and once the pressure equalizes enough the valve closes again. As the air going through the evaporator cools off the pressure on the evaporator side of the valve will change enough to allow the valve to open again to let more refrigerant in. This is perfectly normal as far as I am aware.

If you're concerned about it then the first thing to do is check the temperature of the air coming out of the vents with the AC on full blast on a moderate day (70 degrees Fahrenheit or about 21C). If I recall correctly it should be around 45F degrees or so (~7C to 8C). If it's much warmer than that then there is some issue, either the charge of refrigerant is too low or too high, or several other reasons.

Another thing to check is the charge level of the refrigerant. You'll either need a dual gauge set specifically meant for AC, or just take it to a shop to have them check the levels. You need to check both the high and low pressure sides to know if the charge level is correct.

But if it feels like the AC is blowing cold air properly then it's probably fine, it doesn't take much for the AC to stop cooling air enough to be noticeable if something is wrong with the system. We just have a noisy AC in the H3's.

Hi Paul
thank for the reply. The AC is working strong! perhaps too strong... In some cases I have to mix the cold air with warm air cause the car looks like a refrigerator!
I will che the refrigerant level and I let to know!

[Clark]

Hi put your fan blower on 1 and drive for a while then listen and see if its hissing of a low whistle sound.