I just my vehicle in the shop and they noticed that the AC was leaking at the condensor nut - where the condensor and pipe meet. We checked the parts catalog and could not see if there was an "O" ring in this fitting. If there is no "O" ring, what part is the most common to fail?

Thanks.

 

It's called a pilot tube fitting and you bet there's an o-ring in there!

 

Should definitely be an o-ring in there. If you have a harbor freight tools by you, they sell nitrile o-ring kits that work for many applications. Otherwise order it from Mazda. Be sure to properly evacuate the system and recover the refrigerant.