Weird problem with A/C?
Weird problem with A/C? My work truck has this problem when at idle it blows hot air but as soon as I start to drive it gets cold. Seems like when the rpms are low it blows hot but when they are high it gets colt. BTW its a 2005 Mack Truck.
Big trucks use an air actuated fan clutch the fan clutch may not be engaging fully allowing it to pull sufficient air over the condensor for adequate a/c performance at idle. It will get more noticable as the outdoor ambient goes up. Since it cools at highway speed the refrigerant charge is very close. Check for the clutch not locking it should roar and pull a signficant amount of air if you engage the high idle, or check for bugs blocking the condensor.
