I already have my suspicions, since my wife's GMC did the same exact thing a few months ago. I hear a slight hissing noise from my dash, when running my A/C. I took the system off AUTO, to see if it was caused by the automated venting system, but it kept doing it. I have noticed it the past week, and its becoming a little more pronounced. System still blows cold. It does seem that it takes the truck longer to get cool in the afternoons lately, but it might be due to it being so hot lately.

My wife's car did the same thing and blew cold air for a while....until the hissing became constant and very loud. Turned out, she had a leak from one of the hoses. Dealer replaced it, and find ever since. I'm thinking my system has likely developed a leak and has reduced system refrigerant pressure.

Any other possibilities?

 

Hi RAPR,

I recommend making an appointment at your dealership so they can check this out for you. Touch base with me once you've received a diagnosis; if you need any assistance from me I'l be happy to look into some options to assist. Please include your name, phone number, VIN, mileage, and preferred servicing dealership in your PM.

Crystal

 

I'm pretty sure your right with guessing low refrigerant. Typical of any air conditioning system you're hearing the refrigerant flow through the expansion valve as a gas, not as a liquid as it would if properly charged.

 

Take it in to the dealer - usually they put dye in the gas and they can usually find the leak pretty quickly

 

I've got an appointment set up for tomorrow morning. Thank you for the replies.

 

Let us know what the service department finds/says.

 

I just go buy a can of refrigerant and top it off. Needs it about once every 18months.

 

Well, I'm about sick and tired of my local dealership (HUB CITY FORD of Lafayette, Louisiana). This is the second time they pulled this kind of crap on me, with not keeping to their schedule when an appointment was made.

I made an appointment and was instructed to drop off my truck yesterday @ 7am. They said it would probably take 3 hours. At 4pm that afternoon, right when my co-worker needed to drop me off, they called asking if it was ok for them to keep my truck overnight, because they haven't even looked at my truck yet! They said they had appointments ahead of me...but my truck was "next in line". I told them NO, it is not ok...bc they said nothing about needing to keep it over a day and did not have transportation planned for that.

I told them that they could at the very least check the pressure of the system. If it was low, add refrigerant with their dye. I told him that if it was a slow leak, they would have to add dye and let me drive around for a couple weeks to identify if/where there was a leak anyways. I know this process would take less than an hour to complete.

When I arrived, they "said" they checked the system and everything was in working order and nothing was needed to be done. The truck still has the slight hiss as before, so I now have my doubts if they truly checked my hi/lo ports for system pressure. It would be nice if they could at least tell me what pressures my system measured at. My system still blows cold air right now, but I plan to take a 900 mile trip this week with my pregnant wife. If it stops blowing cold air in this hot Louisiana air, I will have hell to deal with.

It would be nice to have someone local that had the hardware to check the refrigerant pressures, so I could have reassurance.

 

I have owned 2 of these and drove craploads of them. Just get a thermometer from a ac supply store and l put it in center duct after driving a bit it should blow 40 degree air on reculate.blower speed on low. Both make the same noise and all others make the same noise. I'm in Bama so it get dang hot here. Obtw they come with a dye in them from the factory. Now in city traffic it will go up some.

 

Have you made sure all the vent diffusers are open? I'm not being a smartass, I know that if one of mine gets closed all the way it makes sort of a hissing sound.

On a side note: my a/c has been acting up intermittently for the last few weeks, was getting worse yesterday in Calif, so while looking to see if maybe the belt was slipping I noticed my Mass Air Flow connector was broken (guessing one of the quicklane guys stepped on it) I pushed it back together as best I could and got back on the road. My a/c has been working perfect from the moment I left the rest area. Coincidence? Maybe, I have no idea how this connector would effect my a/c.

 

In reality a properly operatimg system with the engine at 1200 rpm's or higher will run app. 25 degrees cooler than ambient. It will usually max out in the high 30's to low 40's.

 

My 2013 has a sound similar to what your talking about too. Sounds kinda like something letting off preasure. I keep forgetting to ask the dealer about it.

My 2011 never made this noise.

 

all my vents are open. I have superman hearing and noticed this sound more recently when the radio is off and the engine is above idle (driving down the road). It sort of sounds like something is exhaling, and it happens roughly every 20 seconds. The noise itself doesn't bother me at all. I just like being able to catch a problem, before it becomes a problem (like being on a roadtrip without AC)...especially since I'm closing in on my 36000 mile warranty.

 

Your discription is just what I thought it sounded like too. Kinda like a person under the dash exhaling. Lol

 

I need to ask the question as to what that sound is too. I just have to remember when I'm at the dealer.