AC hissing noise and warm air.

[ItsJoseV]

12’ Ram 1500.

Lately been having a hissing noise thst randomly appears when the A/C is on near the passenger side dash: Recharged it and worked, then a week goes by and I get the hissing again and now blows warm again. I’m thinking it’s a leak, or a bad evap but before I go full diagnosing on it, wanted to see if anyone else has had this issue?

Edit: Thanks for everyone’s advice. Im heavy duty/automotive mechanic and just haven’t found one that hisses like this until now. I injected oil, and found the leak coming from the evaporator. Thanks again.

 

[indept]

Sounds like a leak. You need a leak detector to diagnose it whether it's a dye that leaves a mess where the leak is or an electronic detector like this one:

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[indept]

Another reason for the dash hissing

 

[GTyankee]

feed that unit a Rat a week, j/k

 

[EdGs]

Another reason for the dash hissing

View attachment 523512

Maybe a little rattling, too.

 

[jws123]

Put dye in the system you will find the leak fairly easy once it leaks out again.

 

[Jeepwalker]

There could be many places it might be leaking. Generally joints, threaded inserts, or front pump seal. There might even be multiple small leaks. If it was the condenser or evaporator, they generally don't last very long till the refrigerant leaks down. In other words, they're usually (though not always) faster leaking. Start with the easy stuff (joints, threaded components, front pump). The front pump seal is often the culprit on older & high-mile rigs. That's a little more difficult to see with dye. The hissing sound sounds like it's the refrigerant equalizing out when the compressor kicks off, or maybe air ..but then I'm not there to hear it so IDK ...just a guess.

Maybe consult with an experienced AC shop if you're not up on it. Rather than start throwing parts at it. They're going to have better tools, more experience and a better eye at locating leaks. Have an understanding that if it is the evaporator, leave it be and you'll replace it (if that's what you're thinking).

Front pump seals can be replaced and often that's a better way to go because A) compressors last a long time and front seals are the #1 leak point on them. B) You don't know what you're getting with a rebuilt compressor, C) With a rebuild compressor you need to ensure the right oil (right type) and the exact right amount is in it before you install it (most people skip this critical step), D) then there's the replacement & refrigeration labor cost of installing a new compressor. And if you get a dud, then ya have more issues to deal with. A shop would have the tools and expertise to replace a pump seal rather quickly. Front seals replacement is great when it works. But even that job isn't foolproof (warning).

Just thinking out loud. Good luck. Let us know what it turns out to be

 

[GTyankee]

The difference between having the dealership or a Radiator Air Conditioning shop do the work is :

The dealership charges a get out of the chair & look at it fee

A private shop just greets you & asks how they can help you

The dealership assigns a Tech that may or may not have worked on A/C units, but they can ask a computer program.

The A/C shop already has an good idea of what is wrong, by what you told them, as you look under the Ram's hood

 

[Tach_tech]

The hissing sound is likely coming from the expansion valve. They will hiss sometimes when the refrigerant level is low.