I have a 2003 Silverado with the 5.3. I noticed the engine becomes much louder when the AC is on. It kind of roars when I drive along kind of sounds like the engine is cold but it is not. It does this most of the time the AC is on and for a while after the air conditioning is off? The dealer said they could not find a thing wrong with it and it is normal fan operation. Does your trucks do this as well? What causes this? Thanks a bunch!

 

the AC drags the motor down a little and makes it work harder to keep the same power level. that's probably why. hell, my AC fan started whinning today...now that sucks.

 

Why would it keep roaring/be loud even after I turn the AC off? Sometimes even after I shut the engine off and later start it up with the AC off and it still roars for a mile or 2 down the road?

 

hmmmm???

 

Maybe just your cooling fan running. Just a thought...

 

With the AC on, the engine gets hotter and activates the fan clutch to spin the fan faster for better cooling. When it cools down, the clutch lets go of the fan and lets it frewheel more.
The roaring is the fan moving tons of air.

 

yep, when that fan is fully engauged it ROARS!! just doing it's job.

 

yea probably just nothing. I noticed my 03 has a tendency to roar with the a/c on, mainly in really hot weather though.

 

Fan Clutch! Get some E-Fans! That fan clutch robs you of like 20 hp during the hot weather!

 

Man fans draw some serious power when they are at full speed. 30A really hits the charging system hard-core. Try turning your fans on manually with the A/C on high and go drive down the freeway. Then turn the fans off but leave the A/C on...there is a huge difference in drag as the alternator is bustinass to keep up.