Occasionally in the summer A/C stops blowing cold air.In winter same w/heater.

What is your question?

Occasionally in the summer the A/C will stop blowing cold air. This does not occur on short trips, but has occurred on longer drives. Typically if the car sits for fifteen minutes or more, the air then blows cold for about ten to fifteen minutes. If the car sits for several hours, then the problem does not manifest unless I drive for 30 to 40 minutes. This winter the same issue seemed to occur at least once with the heater, i.e. it did not blow hot air, only cold air. What needs to be checked? About how much should that cost to: a. diagnose? b. repair? What repair shops near Fairfax, VA can you recommend?

What makes this problem better or worse?

Driving longer distances/times seems to aggravate the issue.

How long has your 2008 Ford Fusion had this problem?

Since last summer although it has not occurred with great frequency.