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Q: Low and high pressures stay low regardless of rpm, even while adding more than required r134a

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Same as above, no cold air, very little drip from evaporator, cold line sweats very little. Compressor runs without any excessive noise. I'm suspecting expansion valve trouble.

Hello. I would need to know more information about the type of vehicle this is to know for sure what is going on. Most of the time though, if you have low pressure on both sides it is caused by low refrigerant. If the refrigerant level is fine, then it is either caused by the expansion valve or the compressor has an internal valve problem. Both can occur and cause this. I usually check the pressures and the line temperatures to determine which one it is. If you are planning on having this AC cooling issue fixed, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the AC system and help you move forward with repairs.

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