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Just a FYI your system is low on refrigerant......the front and rear share the same Freon. That is why it takes a short while to recover.

For what its worth if you have rear a\c you should run it whenever you run the front. The system is designed to run together and has enough refrigerant to do so when charged correctly. The efficiency of this system is flawless when both systems are working correctly. :D
Thanks I'll try again! Maybe I didn't have the rear system on during the last charging?
 

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Thanks I'll try again! Maybe I didn't have the rear system on during the last charging?
Thanks, its fixed.

Turns out, when I hooked up the pressure gauge with both systems running, it showed pressure at the top of the intended fill range. So I added a little more refrigerant to see if it helped. The idle started cycling, the compressor was kicking on and off every few secs, and the AC blew even warmer. Ah ha, so I bled the system to the bottom of the fill range and like magic, both front and back AC blow cold. It was overcharged, I had no idea that could make the back system (only) blow warm.

Thanks for the idea that the refrigerant level was the cause, you were right!
 

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2004 Armada LE 4x4 - Still runs like new!
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Thanks, its fixed.

Turns out, when I hooked up the pressure gauge with both systems running, it showed pressure at the top of the intended fill range. So I added a little more refrigerant to see if it helped. The idle started cycling, the compressor was kicking on and off every few secs, and the AC blew even warmer. Ah ha, so I bled the system to the bottom of the fill range and like magic, both front and back AC blow cold. It was overcharged, I had no idea that could make the back system (only) blow warm.

Thanks for the idea that the refrigerant level was the cause, you were right!
I found some florescent green A/C oil on the garage floor beneath the rear passenger side of my 2004 Amada 4X4 LE. I found a very small spot worn through the 5/16 inch A/C line from a black cable that was chaffing against it all these years, just like with a couple of other posts I've read here. Poor design! You can see it in the attached picture right where the little bubble is. So, I'm in the process of repairing a small section of this 5/16 inch line, evacuating, adding oil and 134.

I assumed that if there was HVAC Pag oil running out of that hole that my refrigerant would have also run out and my system would be empty. To my surprise I found that it was still under pressure when I pressed the Schrader valve on the lower pressure line. How could there still be pressurized refrigerant if the oil is leaking out???
 

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2008 QX56
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Not so cold AC!

Okay, let me see if I can help. I have been in the AC business for 31 years, so let me see if I can explain this in simple terms. Sounds like your AC is fine. Your Armada or for that matter any AC unit is putting out a certain btu capacity at a given temperature. Let's say the unit is designed to be a 12,000 btu's or what we call a 1 ton system at a 95 degree out door temperature. As the outdoor temperature increases the capacity of the AC unit goes down. The hotter it is outside the less efficient the AC system is. This applies to all AC systems period.
The only way this can be over come is for manufacturers to put in a much larger system to compensate for those very hot days. The downside to that is that if you over size an AC system, the cost of the unit goes up and on days where it's not so hot, the unit is now over sized. An over sized unit then causes the compressor to cool to quickly or what we call short cycle and then the compressor wears more quickly, and when you run short cycles, you will not be comfortable because the AC unit doesn't run long enough, therefore it doesn't remove moisture very well, so you have a cool car, but a humid one. In short, it basically goes like this, the hotter it is outside, the smaller your AC becomes. When temperatures go down, you will feel the AC system working like it used to, it's just not designed for those extreme days. The best a mechanical AC system can give you is a 20 degree split. Hope this helps better understand AC systems. Enjoy Las Vegas.


:temphot:
Hi, I was experiencing the same issue, not cooling enough in high Florida temperatures, so I found out my a/c outside fan or I think its called an a/c condenser fan wasn't working as it usually did, so I took it to a shop, the mechanic checked it, did something then it worked. He charged me $65, he said it was to replace 1.5 lbs of missing freon and that the 2008 QX56 a/c condenser fan doesn't come on if the system is low on freon. Is that true?

Also its been about a month or so later and today the same issue happened again, the fan stopped working and the air isn't cooling much, so I went to check next to the radiator where I would connect the freon hose, I unscrewed the black cap and heard an air pressure release sound, simply from unscrewing / opening the black cap that covers the A/C low-pressure service port. Is that normal? Cause I have done this before on another vehicle and don't recall any air pressure release sounding noise when just unscrewing and removing the black cap.

Edit: a couple of months earlier I had gone to this shop to get other work done, then awhile later this a/c issue started. Prior to this I never had any issues with the a/c. Also, seems strange that at the time the freon was recharged, there was no attempt to correct the leak cause or to find the cause of the leak.

So...
A.
Is it true that the 2008 QX56 a/c condenser fan doesn't come on if the system is low on freon?

B. Is it normal to have a leak or pressure release sound when opening the A/C low-pressure service port cap? Especially after the tech just used that port to recharge the system?

Thanks a lot
 
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