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Hi everyone, I am in Florida and my 2008 QX56 a/c suddenly wasn't cooling enough, so I noticed my a/c external fan or I think its called an a/c condenser fan, located in front of the radiator and condenser wasn't coming on as it usually did, so I took it to a shop thinking maybe a fuse or something simple, 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.

A. 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 to see if mine would fit for a recharge, 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.

B. Is that normal?

Note:
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.

Your opinion and any advice is greatly appreciated!

Thanks a lot
 

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first off welcome.

i must stress , if you dont know anything about the HVAC system please do not interfere with it. you can cause damage to your system and you can also cause physical injury to yourself or other persons nearby. the system is under pressure and if you are attempting to put refrigerant into your system into the wrong port, it can be disastrous.

the system has sensors on it and the system has a high and low side. they both must be in equilibrium.if there are any huge pressure differences, the system has sensors to prevent it from working so yes the fan may not turn on at times. this could also mean you have a faulty sensor.

you clearly have a leak in your system. the person you took it to just filled it up. they should have done a leak test (assuming they didn't since they only refilled your system).

when you open up the high or low side on the system, there is a nipple in there similar ro a bicycle tire. there should not be any release of refrigerant into the atmosphere if you simply remove the protective cap.

just looks like you have issues with your system and perhaps the mechanic damaged or exacerbated something along the way.
 

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Here is some info about that fan and its operation as well (from an old thread I found):

The condenser fan is controlled by the ECU. The relay is inside the IPDM, and isn't accessible. The ECU looks at the engine rpm, battery voltage, vehicle speed, coolant temperature, A/C on or off, and refrigerant pressure. By reading all these inputs the ECU controls the fan.

This is the basic operation of the fan:

When the A/C is turned off the fan will operate only when the coolant temperature is above 212F AND vehicle speed is less than 25 MPH, OR when the coolant is above 221F AND speed is over 25 MPH.

When the A/C is on, the fan operates when the refrigerant pressure is above 226 PSI. Vehicle speed isn't a factor when A/C is on.
 
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