05 Impreza AC cycles on and goes PSSST

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2005 Subaru Impreza with about 95K miles on it. When the AC is on, it cycles on and off every 30 seconds or so, when it cycles on it sounds almost like a blow off valve PPSSST

AC works fine, blows very cold. What would cause the compressor to make a PSSST sound?

Other than the pssst sound, the car's AC feels great.
 
On Subaru Vehicles compressor cycling is normal operation, as long as its cold and not cycling every 5 seconds there is no problem. Cycling times will vary with ambient air temp.

Edit: I don't know if this normal on the latest models as I have little experience with them.
 
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Everything works fine. The question at hand is if this is a sign of something. I've only had the car for about 10k miles and the AC rarely used. Now that my wife is driving it and the kids can finally go in it, the ac is always on, which is why I noticed it. Might be nothing. As AC systems tend to cycle often to keep from freezing. It's just weird to me that it goes psst.

Not planning on taking it in to a shop unless there's reason to believe something could be wrong. Just trying to get some opinions from anyone they might know AC systems.
 
If its cold I wouldn't worry about it, these Subaru's have all sort of little quirks and engine noises that on another engine would mean impending certain doom but on these its normal e.g what sounds like a rod knock at idle (it isn't).
Do watch out for head gasket issues, very easy job on these but a common failure point.
 
Cycling is normal as mentioned, but maybe the clutch plate is dragging for a few moments once the clutch cycles off? That would account for the noise you had mentioned. If so, it's likely a sign that the A/C clutch springs are getting weak and the will start dragging all of the time when the A/C compressor is not engaged.
 
Originally Posted By: jeffie7
2005 Subaru Impreza with about 95K miles on it. When the AC is on, it cycles on and off every 30 seconds or so, when it cycles on it sounds almost like a blow off valve PPSSST

AC works fine, blows very cold. What would cause the compressor to make a PSSST sound?

Other than the pssst sound, the car's AC feels great.



If you hear that inside the car, you're low on charge. The compressed and condensed coolant is already vaporizing before it reaches the evaporator.

If you hear it under the hood, I don't know what you're hearing exactly, but I suppose the low charge could be heard there aswell.
 
Originally Posted By: Jetronic
If you hear that inside the car, you're low on charge. The compressed and condensed coolant is already vaporizing before it reaches the evaporator.

I'm no A/C expert but my Accord made a psssst noise from the A/C as well. It was inside the cabin and seemed to coincide with the compressor cycling. After I topped off the system (was a little low), the noise almost disappeared; only hear it now on the hottest days when idling.
 
Eric the car guy has a nice AC condenser cleaning video which shows how much internal pressure changes when you clean the condenser even if the interior temps aren't affected much. It will cycle less with a fully cleaned system
 
Originally Posted By: 901Memphis
Eric the car guy has a nice AC condenser cleaning video which shows how much internal pressure changes when you clean the condenser even if the interior temps aren't affected much. It will cycle less with a fully cleaned system


Watched his video and ended up using this.

Simple Green Foaming Coil Cleaner.


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It still makes the Psssst noise but it's much much less noticeable and less frequent. When I get a chance I'm going to run up to the local AC shop and have the system checked to see if its over/under charged.

Regardless, clearly the cleaning helped.
 
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I have a subaru too, a legacy, and from what I've heard they are super picky about how much refrigerant is in the system. If you take it to a shop, make sure they know subaru's and put the correct amount of refrigerant in.

I didn't have anyone touch the AC system in my '09 legacy until I hit around 200k and it seemed like my AC wasn't as cool as it should be. Had the dealer do an AC system service, and it was the same after. I think it was just the heatwave we had last summer, car just couldn't get the air as cold as I thought and would have liked.
 
Just wanted to give an update, I finally had a chance to take the car into the shop to have the AC system inspected. The system was low on refrigerant. After having the system recharged and dye added they ran the car for awhile and could not find any signs of a leak, I was asked to bring it back after a few weeks to recheck for the leak.

No more Psssst sound.
 
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