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My 2004 Buick century is having AC problems while I'm sitting in idle my car AC blows ice cold air but once I start to drive at about 35mph it starts to blow warm air and when I stop at a light or put the car in park it starts to blow ice cold again does anyone know why this is happening?

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  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Jul 3 '18 at 22:00
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    Any recent r134 added? – Milison Jul 3 '18 at 22:14
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    While parked try revving your engine and holding it at high RPM, does it stay cold or blow hot? – GdD Jul 4 '18 at 7:26
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    Is it an Harrison V5/V7 compressor? If so, it may be destroking too much once the RPM rise up (control valve problem). You can also try having someone watch the AC clutch and check if it's disengaging when you rev from stationary, or someone revving from inside while you're watching it. – Al_ Jul 4 '18 at 13:41
  • Checking if it's an Harrison V5/V7 compressor is vital because these compressors can start behaving strange when the refrigerant charge becomes low (aside from damage due to low lubrication rate). These ones have a valve that makes them pump less or more in order to maintain a precise suction pressure and that's also why they lack a low pressure sensor or switch. They're designed to work with a precise charge weight: lower the charge and they can destroke much earlier than they should (increasing the suction pressure and the evaporator's temperature along with it). Only charge them by weight. – Al_ Jul 4 '18 at 18:55

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