I just had am a/c unit replaced in my 1997 F150 5.4 engine and have just noticed a chirping sound under acceleration about 1500 rpm. Sound seems to be coming from the belt? Only happens under acceleration, not at idle. Could this be related to them changing the a/c ? I have a 2yr warranty. It wasn't there before I had the a/c fixed. Any advice?

 

Bring it to the shops attention that a new sound has come about since the new ac installation. Take them for a ride and let them listen. They should, as the installer, find whether its the belt, from the install or possibly the pump itself.