2002 Ford F-150 King Ranch 8 Cyl 5.40L
Body & Interior
Air (AC) comes out of the defrost vents when I am loading the engine or going up hill etc.
When i am just cruisin down the hwy and am keeping up with traffic the AC blows normal, but when I go faster or put any strain on the engine it tends to blow out the defrost.
ASE MASTER MECHANIC TEXAS 1/17/2011
Your a/c in your dash works on vacum, more you give it gas, less vacum at the port for your A/c ducts.