I have a buzzing noise coming from the back when A/C is on.
Any ideas?

 

Buzzing from where? The back of the AC grill or the back of the inside of the car? Not that I could advice you, but just wondering. From the blower motor?

 

I have not checked but I will, for know it comes from the back of the car and it was until recently that I realized that it was when the a/c was turned on.
I will check!

 

Sounds like the belt.

 

I checked and I can't hear anything weird in the back with the lid open, if you close the lid and get into the car you hear it.
Would the a/c compressor make that noise? It is working fine but what else would it be? I thought also about the belt but you would hear it with the engine and a/c running with lid open right?
Anyways thanks to all of you for your help I will keep checking and let you know what I find, have and excellent day!

 

I recently (two weeks ago) had a similar sound. Replaced the belt (5 minutes, very easy to replace), sound gone!