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2012 Hyundai Sonata Manual Transmission A/C only blows cold when RPM is up

The A/c system is only blowing cold air when the RPM of the vehicle is up. When stopped, if the car is put in neutral and RPM increased to about 1.5-2000 the a/c will begin to blow cold. It also blows cold while the vehicle is moving.

Butting sitting at a traffic light in neutral without RPM it will blow uncooled warm air (south florida). We checked the 134a and it was in the red on the gauge. The condenser fan seems to be spinning at all times. I cannot get a could view of the compressor but it seems to be always spinning regardless if the A/C system is on or off.

Any ideas?

Could you please explain that?



We attached a pressure gauge to the low pressure coolant line. The gauge said it was full.

What type of pressure gauge?


Its the gauge that comes on the A/C Pro refrigerant recharge. We thought the refriderant might be low. But the gauge stayed in the “red” full when the car was off and on with the a/c running full power.

The gauge should be in the green zone if the system is charged properly with the AC on.

Did you follow the instructions?

The only way to tell what’s actually happening with the AC system is to connect a set of manifold gauges to determine what the pressures are on both the low and high sides.

Doing anything else is just guessing.


We didn’t actually add any refrigerant to it. We only used the gauge on it. Do you think the refrigerant is the issue?

The only way to tell is to connect a set of manifold gauges to the system like the one I showed.