[B and C]

Went to RV yesterday and found air system completely down.  Located a leak in the 120V compressor compartment on a small silver/black component on the sidewall.  It is about 2 inches long by 1 inch wide, mounted to the sidewall near the compressor with two plug on electrical connections and an air supply from the compressor exhaust(?) side. The air supply runs through another component before reaching the part leaking.  There is a full-blown air leak from the bottom of this small component which has drained the entire system. 
I have tried to post pictures but obviously need some guidance on how to post.
Thanks!!

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This is another picture with the part in question outlined by the crude blue box.
Thank you.