I notice when I'm using the A/C (4.6) and I down shift into a lower gear (passing), the A/C defaults to the defrost and then back to the front vents once I go back to over drive. Is this due to lack of A/C vacuum on these newer trucks.

Thanks.

 

Sounds like you have a vacuum problem. Probably a leak somewhere that's just big enough to affect the a/c when you hit the gas.

 

I thought that was the problem too, I contacted a sevice manager and of course he told me that was normal for these newer trucks due to less vaccum capacitie????

Thank you!!