AC suddenly stopped blowing cold air, 2011 Audi A6 Quattro

[Sussib]

Hi,

I have a 2011 Audi A6 Quattro 3.0T and the AC has worked perfect, blowing ice cold air. Last week while I was driving, I heard a slight high pitch "whistle" sound and I pushed the ON/OFF button to turn off my AC to see if the sound disappeared (which it did). When I turned the AC system back on, it no longer blows cold air. The fan works, but the air is warm. I brought it to an AC repair place and the guy ran the code and told me it showed the error "00256 High Pressure Switch/Sensor" and that he wasn't 100% sure this would fix the issue, but he was pretty sure. Long story short, he installed the new switch and the compressor still would not kick in. He was also unable to clear the code, ie it kept coming back right after clearing it. So I brought it to another guy to have them "diagnose" it and he just told me the same thing "Oh it shows error code 00256 so I would have to install a new high pressure switch and see what happens". He wanted $700 to do this, with no guarantees of anything working so I obviously said no.

I was hoping someone could give me some tips of what this could be. For example is there any type of relay etc for the AC compressor? Why would it all of a sudden just stop working after pressing the ON/OFF button? Any advice would be greatly appreciated! Thanks.

[LionKing]

Sounds like it's low on refrigerant, you have a leak somewhere.

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[Sussib]

Sounds like it's low on refrigerant, you have a leak somewhere.

Sent from my Pixel 6 using Audizine Forum mobile app

No, it's not low on refrigerant because the mechanic that installed the switch, checked the refrigerant level as well...

[Tai-Lun]

I had a similar issue, we went through all of the parts. It turned out to be a hairline fracture in the condenser as well as the lines, after both were replaced the AC blew cold again.

However, I STILL have a bit of a whine from the AC lines right up on the driver side strut tower. Everything is tight, OEM parts... so it may be a very tiny leak still. I have no codes anymore, just the tiny hissing.

[Sussib]

I had a similar issue, we went through all of the parts. It turned out to be a hairline fracture in the condenser as well as the lines, after both were replaced the AC blew cold again.

However, I STILL have a bit of a whine from the AC lines right up on the driver side strut tower. Everything is tight, OEM parts... so it may be a very tiny leak still. I have no codes anymore, just the tiny hissing.

Thanks for the info. Do you know if your car threw the same code for the High Pressure Switch (#00256)?

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[Tai-Lun]

I don't no, I looked to see if I had a photo from then but I unfortunately don't.