My 2004 F-150 XLT SCab's airconditioning works great when I am moving, but when I come to a stop light and idle all I get is hot air. This even happens in the winter, the compressor is running but no cold air. I checked the freon and it is good. Anyone suggest where I can start or an approach, besides going to the Ford dealer who sold me the vehicle with the problem "AS IS" of course, my last resort.

 

only a guess ,maybe you have a vacuum leak letting damper door a idle close off the ac coil.(evaporator) under the dash some where. when the engine is running at a higher rpm maybe enough vacuum to open the damper door .this is only a theory. good luck.

 

This is another hunch: how is the engine coolant level?

 

I have tried increasing the engine speed while at idle up to 2500 rpm thinking it was engine speed that caused the cut out, but no difference until I start moving above 45 MPH.

Engine coolant level is full, I changed it recently when the radiator hose blew off, love those factory hose spring clamps.

Someone stated that the heater control switches inside the vehicle were infamous for going bad, but not sure how to trouble shoot.

 

Just FYI you are in an Explorer forum here. I don't know much about those, perhaps other folks in here do though...

The Explorers have vacuum operated components in the heat/ac delivery system. The doors (dampers) that direct where the heat/ac airflow comes out are vacuum operated. To prevent those doors from moving when the engine is at idle there is a vacuum reservoir in the system. In the Explorers it is located up under the dash on the passenger side. Maybe the vacuum reservoir in your F150 is leaking, but I don't know where it is located.

 

one more suggestion= check your engine cooling fan-it sounds like it is not drawing enough air thru the condenser which would cause the problem you describe. to check it run water from a garden hose or air from a box fan over the condenser and if the a/c blows colder then likely this is your problem. also make sure the system is correctly charged as an overcharge of 134a will cause the system to cool poorly.
jim

 

Moved to appropriate forum.