Car air conditioning system operates in the following patterns. Initially cold air comes out the a/c vents then after a while warm air comes out the a/c vents.
Car Problem Diagnosis
A/C system has a component called an expansion valve. The expansion valve controls the amount of refrigerant that flows into the evaporator. If the expansion valve is blocked the refrigerant will stop flowing into the evaporator, if this happens the a/c system will only produce warm air. What causes blocking on the expansion valve? Well, after the car a/c is turned on the expansion valve starts to freeze, soon after it will totally freezes up and causing the blocking of refrigerant that flows into the evaporator. An expansion valve will freezes up when there is moisture in the refrigerant. This moisture will accumulate into the expansion valve and freezes there thus creating a block on the valve.
Possible Cause of Air conditioning Problem
A/c expansion valve freezes up
All About Auto Recommendation
Bring the car to a reputable shop specialized in car air conditioning system. Ask the mechanic to check the a/c system for leak this is probably the cause why moisture gets into the refrigerant. Once the leak is detected the mechanic will remove the refrigerant then repair the leak including the replacement of the component called the receiver/dryer and then refill the system with a new refrigerant.
Probably there is no problem with the expansion valve the real problem is the moisture content of the refrigerant. You might be wondering why the receiver/dryer is replaced? The receiver/dryer is the one that removes moisture from the refrigerant, since the expansion valve freezes up because of moisture then it means that the receiver/dryer is not functioning properly that is why the car a/c system initially blows cold air then soon after it blows warm air.