Car A/C Initially Blows Cold Air then Followed by Warm Air

Car Trouble Symptoms
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.
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