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Discussion Starter · #1 ·
Hello

I own an 08 frontier crew cab with long bed 4.0L 24000 miles. I recently have noticed a periodic (every few minutes the hotter the more often) hiss coming from under the dash on the passenger side. it only happens when using the A/C. it doesn't seem to matter what AC mode its in. The AC works great, even in this summer 90+ degree heat. was just wondering if it may indicate something wrong or going wrong. I never noticed it before since i bought it two years ago. it is also kind of annoying. anyone else with this scenario?
 

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Hello

I own an 08 frontier crew cab with long bed 4.0L 24000 miles. I recently have noticed a periodic (every few minutes the hotter the more often) hiss coming from under the dash on the passenger side. it only happens when using the A/C. it doesn't seem to matter what AC mode its in. The AC works great, even in this summer 90+ degree heat. was just wondering if it may indicate something wrong or going wrong. I never noticed it before since i bought it two years ago. it is also kind of annoying. anyone else with this scenario?
You sure your not hearing the radiator cooling fan when it kicks in? Just a thought.
 

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My 06 does the exact same thing. I think its the refridgerant going through the expansion valve under the dash, bu I'm not 100% positive
 

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Usually when you hear the AC hiss it means you are low on freon, worth a check.
 

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Discussion Starter · #5 ·
You sure your not hearing the radiator cooling fan when it kicks in? Just a thought.
definitely not the fan. i can tell the difference. 2 distinct sounds. it definitely has a liquidy sound to it. like when my home air handler starts up just not as loud
 

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Yep, I got the same exact thing going on.

It makes this sound every time the AC pump engages. The AC in my truck works fantastic, but mentioned above, it really may be low. We who have this noise going on should get it checked.

It kind of a liquidy swirly hissing noise, sounds kind of cool if you ask me, but its definitely the refrigerant expanding passing through a pressure valve like mentioned above.
 

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"A/C hiss"

Hello

I own an 08 frontier crew cab with long bed 4.0L 24000 miles. I recently have noticed a periodic (every few minutes the hotter the more often) hiss coming from under the dash on the passenger side. it only happens when using the A/C. it doesn't seem to matter what AC mode its in. The AC works great, even in this summer 90+ degree heat. was just wondering if it may indicate something wrong or going wrong. I never noticed it before since i bought it two years ago. it is also kind of annoying. anyone else with this scenario?
Had the same thing happen earlier today. Hadn't noticed it before when operating the A/C, but today experiencing high humidity (70% + ). Also noticed a high degree of condensation drain in the driveway for the first time.
 

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My '09 does it, but only when it gets really hot out (ie 100 plus). I don't think I'm low on refrigerant, but I guess I'll check it out. If anyone actually does take the truck in to Nissan, let us know what they say about it.
 

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i just gave my system a 1 pound can of reefer that bumped it back up,i got it new in 06 so i used the ac 3 seasons,did it with the gauge hose set up from the zone,it blows snow flakes now
 

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definitely not the fan. i can tell the difference. 2 distinct sounds. it definitely has a liquidy sound to it. like when my home air handler starts up just not as loud
It does make sense, about refrigerant running through the expansion valve. It's turning from a high pressure liquid to a low pressure gas at that point. As hot and humid as the weather has been lately, the A/C system is doing all it can to keep up. Do check your charge though, could be low somewhat.
 

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Mine does it- was curious if it could be low since the compressor does cycle quite often, even on low fan speeds and not full cold.

Let us know what you find out.
 

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OK, kinda slow at work today so I hooked it up to the recover/recharge machine. Like others, mine was blowing pretty cold(i'd like it colder, but 134a sucks to beging with). I recovered all of the refridgerant and I was .1 lbs or 1.6 oz low. System held a vacuum for 30 minutes. Recharged it back to spec and it still does the same thing, and the temp didnt change from the center vents. I really think it's normal.
 

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Mine does it only when it is really hot out.

I have been told by the dealer it is normal (something about the cycling process).

I think it is annoying, but I can't hear it with music on.
 

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I gotta believe the noise you guys are hearing is the refrigerant turning from a high pressure gas to a low pressure gas in the evaporater. At the same time, it's boiling the moisture in the air out and exchanging heat as the air passes through the evaporater. This may sound stupid but, check to see that the in-cabin air filters are in place. It may muffle the sound and slow down the volume and speed of the air flow through the evaporater, so it doesn't work as hard. Just a thought, as there were none in my truck when I bought mine new. Also, try putting the switch in the recirculate position, see if it helps.
 
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