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My 2015 Chevrolet Silverado is blowing only hot air when having the AC on. Looking for possible answers what might be the problem. The compressor is working, because when I add R134a to the system it clicked in and turned on. I believe there is a leak in the system, so I put dye through the system and followed the lines and components with a UV light and cannot find a leak. The system gets cold for a day when I add the refrigerant, maybe 2 days at the most, then back to blowing hot air. I took a set of manifold gauges and took the pressure readings to diagnose the problem through gauge readings. I hooked up the gauges and with out the vehicle running the pressure was equal like it should be ( not sure if reading was right, I will look it up in my vehicle manual) but it was 85 on both the high and low gauge, is equal readings as normal, meaning the equal each other out, which is normal before the vehicle is running. I started the vehicle and took my readings and they seemed normal also, 25 on low and 145 to 150 (depending on compressor kicking in and out), so normal readings from my understanding. So if there was a leak, the low side should be reading close to 0 or slightly in the negative if the system is low correct? So I am at a loss if the system is not leaking, why would it be blowing hot? I am at a loss, so if anyone has any ideas that would be helpful on what else to check or that it might be, I would appreciate it. Thank You

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    Welcome to Motor Vehicle Maintenance & Repair! I think you've already solved your issue, you just need to find the leak. If you lose pressure over time, you have a leak. Find the leak and you can fix your issue. Just because you can't find the UV, doesn't mean it isn't leaking. You need to look harder for it. – Pᴀᴜʟsᴛᴇʀ2 Aug 22 '20 at 23:30

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