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My 2004 Mazda 3S 2.3L Hatchback A/C has recently started cutting out when you accelerate. When its idling A/C works fine. When I say cut out I mean the compressor cuts off and on while accelerating but not while idling. This happens at any accelerating RPM or any load. I checked the refrigerant charge and thats good. Could this be a pressure switch or do I have another problem. I changed the fan switch last year due to my a/c light cutting in and out causing the compressor to cut on and off. Thank you.

  • How did you check the refrigerant charge? I would tape a manifold gauge set to the windshield, and test. You might find under load the low side dips below the cutoff for the pressure switch. Keep in mind at WOT "wide open throttle" most modern ECU vehicles disable the compressor for maximum power. I get that you have a different situation, but I'll bet the compressor is "sucking" the low side below the cutoff point. – SteveRacer May 8 at 3:33
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How did you check the refrigerant charge? Did you only look at the pressures or weigh it?

The only reliable method of checking the refrigerant charge is evacuating the system and weighing the charge contained inside. Any other method is unreliable.

A low charge weight can, and in fact will, give static pressures and idle pressures that are good enough for a LP switch to enable the clutch, but too low for the clutch to stay engaged long enough when accelerating if the switch is located on the low pressure side (unusual in systems that feature TXVs and evaporator temperature sensors, like the ones on Japanese cars equipped with scroll/through vane compressors).

Do you hear hissing noises from under the footwell when you run the AC?

Out of curiosity, can you see a pressure sensor/switch on the low pressure side too, or do you see one only on the high pressure side?

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