Does the control panel switch to 'econ' when the compressor cuts off, auto mode being unselectable? Charging to 40 psi, is that a static pressure, or the low side pressure when the compressor runs? Typically, the a/c system is charged by weight, not pressure. Your system would require 2.0 lbs of refrigerant. The system pressure when static, almost equals ambient temperature, so if it is 40 degrees outside, and the system is not running, then the pressure may read 40 psi. What does the pressure do when the compressor cycles on? Assuming you are tapped to the low side, it should drop. If it drops too fast, and below 20 almost to zero, then it may be undercharged. Does it display a message on the info center, perhaps A/C OFF-LOW REFRIGERANT, or SERVICE A/C SYSTEM?
This guide can help us fix it
https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak
Please run down this guide and report back.
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Friday, May 7th, 2010 AT 11:26 PM