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Hello everyone, new to jeeps and to this site.

So I bought a used 2017 Jeep Grand Cherokee Limited. When the A/c is running I can hear a hissing noise on the inside of the vehicle. The A/C works good and is cooling. If I increase the idle the sound is much less, bring it back to idle and its louder.

Do you think it may be low on freon? Could it be something else? Any help would be appreciated.

Thank you
yes you are loosing Freon; it means you have a leak
 

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Hello everyone, new to jeeps and to this site.

So I bought a used 2017 Jeep Grand Cherokee Limited. When the A/c is running I can hear a hissing noise on the inside of the vehicle. The A/C works good and is cooling. If I increase the idle the sound is much less, bring it back to idle and its louder.

Do you think it may be low on freon? Could it be something else? Any help would be appreciated.

Thank you
Could also be a vacuum leak behind the dash.
 

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Freon is a brand name for R-12, that was phased out long ago. Refrigerant is the name of the working fluid for AC systems. Yes, we know what you mean, Cleanex is tissue.

Well that was a waste of time! I took it to Pep Boys and the hissing sound mysteriously went away. Service worker said noting was wrong because it is blowing cold air. Besides that they can't check Dodge, Jeep, etc because they do not have he fitting to connect to our vehicles. I was trying to save a few bucks vs the dealer. As soon as I drive away the hissing is back. No I didn't turn around because they can't connect their ac fitting. So on to the next one. Stay tuned! I'm believe that freon is leaking from the condenser lines. I see green around the ends of the lines.
FCA/Chrysler/Dodge/Jeep/Ram all use the same fittings as everyone else. Jeep has recently switched to the new refrigerant R-1234yf, that has new fittings as reference design spec to prevent mistakes in servicing. So more likely Pep Boys doesn't have the fittings for the newer R-1234yf systems.

Could also be a vacuum leak behind the dash.
Josh is right, there is no engine vacuum plumbed to under the dash that I am aware of. The HVAC uses electric actuators/motors to move air blend and mode doors....
 

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Hello everyone, new to jeeps and to this site.

So I bought a used 2017 Jeep Grand Cherokee Limited. When the A/c is running I can hear a hissing noise on the inside of the vehicle. The A/C works good and is cooling. If I increase the idle the sound is much less, bring it back to idle and its louder.
That's one is afaulty fan inside the dust board
 

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My '13 was making the same noise for a while and then cooling became inadequate. I added refrigerant myself (from auto parts), it was simple. No more noise, cools fine.
 

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Hmm, my 2020 Trailhawk is making faint hissing noises in AC like this recently too. It sort of sounds like a tiny Darth Vader is sitting in the AC ducts. It is still cooling quite well, so I am reluctant to take it to the dealer in these crazy times.
 

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Hmm, my 2020 Trailhawk is making faint hissing noises in AC like this recently too. It sort of sounds like a tiny Darth Vader is sitting in the AC ducts. It is still cooling quite well, so I am reluctant to take it to the dealer in these crazy times.
First check it with the AC off and make sure the sound is actually the AC or another part of the system.... ....the filter or blower fan can make noises, and those are much easier and cheaper to repair than the AC....

I thought I had a bad blower fan, the noises really sounded like a squeaking bearing.... ....replaced the cabin air filter and the noise never came back....

If you're AC is low on refrigerant it changes how it flows through the system, just being low on refrigerant can cause the noises.... ....I've seen multiple posts recently of folks saying the having their system serviced and topped of on refrigerant resulting in ending the noises..... ...yea, a 2020 shouldn't be leaking refrigerant already, it should be covered under warranty...
 

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Well, I will experiment with it a bit.
I have some noise in the back of the car that sounds like a screw rolling back and forth in some channel when I accelerate and brake hard, so I am waiting for it to piss me off enough to take it to the dealer. I must be annoyed with this stuff enough to build enough motivation to take the car to the dealer and deal with a day or more without the car probably.
 

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Discussion Starter #32
Hmm, my 2020 Trailhawk is making faint hissing noises in AC like this recently too. It sort of sounds like a tiny Darth Vader is sitting in the AC ducts. It is still cooling quite well, so I am reluctant to take it to the dealer in these crazy times.
Thats where Im at as well.
 

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Sorry everyone for the delay in responding. For some reason I stopped getting email notifications from this post. I logged on and was happy to see so many responding. I will dig a little deeper and see what's going on with it. Thank you so much for your advise.

So new thoughts, the refrigerant is put in the the low side line, is there settings I should know about to fill?
 

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Sorry everyone for the delay in responding. For some reason I stopped getting email notifications from this post. I logged on and was happy to see so many responding. I will dig a little deeper and see what's going on with it. Thank you so much for your advise.

So new thoughts, the refrigerant is put in the the low side line, is there settings I should know about to fill?
If you are going to try to DIY get a kit that has a built in pressure gauge and trigger handle. If it's still cooling now but you suspect it might be low you will almost assuredly not need more than one can of refrigerant. Yes it hooks to the low side. The fitting on the kit hose will only fit the low side fitting on the vehicle. The kit should have sufficient directions to get you going. I usually use a full gauge set but last time I just used a kit my ex son in law left. I don't know if the gauge was inaccurate or if system pressures for the JGC are different than I normally see but I would have expected a low side pressure with the vehicle running of about 33 but it was running around 40. I put in about 3/4 of a can and it was still running around 40 but seemed to be just a tiny bit going up. Generally when you are getting to the point where you are putting too much refrigerant in you start to see the low side pressure go up. If you get too much in you get high pressures in the system and get worse cooling at higher speeds. Obviously you don't want that so the goal isn't to get as much refrigerant in as possible but to get the right amount in. You can always add more later.. I don't like bleeding it out (it's bad for the environment) and you usually lose some of the oil when you bleed freon so better to just put a reasonable amount in and see if it appears to be enough.
 

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Sorry everyone for the delay in responding. For some reason I stopped getting email notifications from this post. I logged on and was happy to see so many responding. I will dig a little deeper and see what's going on with it. Thank you so much for your advise.

So new thoughts, the refrigerant is put in the the low side line, is there settings I should know about to fill?
You really need a set of AC gauges to service an AC system properly. The FSM does have a table of ambient conditions at resulting high/low pressure, but it breaks it up into pretty broad chunks... ...that is what I suspect is behind dealers telling folks with signs of low refrigerant it tests good....

DIY AC servicing without the proper tools and knowledge can be risky... ...folks have done it and didn't damage their AC system....

But consider the potential cost of an AC repair vs going to professional AC shop charges for service....

If you decide to DIY, the pressures are tested at 1000rpm on the engine.... ...low side pressure should be around 30psi or lower, going to as much as 40psi for ambient around 100°F... ...one nice thing about the WK2, it will throw CEL and fault code for High Side Pressures being too high, thus warning you that you overserviced the system, but you need a way to read the codes....

If you have AlfaOBD or DiagFCA, you can pull up the sensor feeds for the AC and somewhat use them as AC gauges... ....the pressure transducer is the high side pressure, the temp sensor is the evaporator and you can convert it to pressure with an R-134a pressure/temp relationship table....
 

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Discussion Starter #36
You really need a set of AC gauges to service an AC system properly. The FSM does have a table of ambient conditions at resulting high/low pressure, but it breaks it up into pretty broad chunks... ...that is what I suspect is behind dealers telling folks with signs of low refrigerant it tests good....

DIY AC servicing without the proper tools and knowledge can be risky... ...folks have done it and didn't damage their AC system....

But consider the potential cost of an AC repair vs going to professional AC shop charges for service....

If you decide to DIY, the pressures are tested at 1000rpm on the engine.... ...low side pressure should be around 30psi or lower, going to as much as 40psi for ambient around 100°F... ...one nice thing about the WK2, it will throw CEL and fault code for High Side Pressures being too high, thus warning you that you overserviced the system, but you need a way to read the codes....

If you have AlfaOBD or DiagFCA, you can pull up the sensor feeds for the AC and somewhat use them as AC gauges... ....the pressure transducer is the high side pressure, the temp sensor is the evaporator and you can convert it to pressure with an R-134a pressure/temp relationship table....
Thanks, my neighbor has gauges but I just may take it in
 

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Thanks, my neighbor has gauges but I just may take it in
If you've got gauges, you should be fine, I've done mine own with gauges and it runs perfectly fine....

Ambient Air Temperature (Apparent)70° F80° F90° F100° F110° F
Maximum Allowable Air Temperature at Center Panel Outlet48° F48° F54° F59° F65° F
Suction Pressure at Service Port (Low Side)20 to 30 psi20 to 30 psi30 to 40 psi30 to 40 psi35 to 45 psi
Discharge Pressure at Service Port (High Side)150 to 250 psi200 to 300 psi225 to 325 psi250 to 350 psi300 to 400 psi

Check with the AC on full / recirculate with all the windows open and engine rpm 1000rpm.

You never mentioned what year your WK2 is, keep in mind the later WK2's switched to a R-1234yf system, this table is for the R-134a system.

Here is recording of my tiny Darth Vader living in the AC ducts New video by Dominik Behr
Yep, it shouldn't make that sound... ...But with AC you really can't tell anything until you put gauges on the system and see what the hi and low side pressures are?

Sure, folks can tell you that is the same sound their system made when it was low on refrigerant. But the next step is too put gauges on it to diagnosis it then add refrigerant if the diagnosis is the system is low on refrigerant....
 

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Well, the car is under warranty. Made an appointment on September 23rd at Normandin. Hopefully they will also find the screw that is rolling somewhere under the floor when I brake and accelerate.
 

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Discussion Starter #40
If you've got gauges, you should be fine, I've done mine own with gauges and it runs perfectly fine....

Ambient Air Temperature (Apparent)70° F80° F90° F100° F110° F
Maximum Allowable Air Temperature at Center Panel Outlet48° F48° F54° F59° F65° F
Suction Pressure at Service Port (Low Side)20 to 30 psi20 to 30 psi30 to 40 psi30 to 40 psi35 to 45 psi
Discharge Pressure at Service Port (High Side)150 to 250 psi200 to 300 psi225 to 325 psi250 to 350 psi300 to 400 psi

Check with the AC on full / recirculate with all the windows open and engine rpm 1000rpm.

You never mentioned what year your WK2 is, keep in mind the later WK2's switched to a R-1234yf system, this table is for the R-134a system.


Yep, it shouldn't make that sound... ...But with AC you really can't tell anything until you put gauges on the system and see what the hi and low side pressures are?

Sure, folks can tell you that is the same sound their system made when it was low on refrigerant. But the next step is too put gauges on it to diagnosis it then add refrigerant if the diagnosis is the system is low on refrigerant....
Mine is a 2017 and it has the new refrigerant, so is there a chart of those numbers?
 
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