Air conditioning cause septic odors

Dear fellow Podders,

Please start reading this post by understanding the following egotistical statement:  I am a very smart guy with three engineering degrees (mechanical, electrical and ship design) from the best engineering schools in the world.  And what else is the R-pod if it is not a ship on the ocean of tarmac?  And, despite my high qualifications and world-beating intelligence, I am stymied by the following conundrum:  why does my air conditioner suck fumes from my black tank?  I’ve already tried the obvious, thank you very much.

Problem description:  “lovely” odors during flushing only when the AC is running.  Does not occur when the AC is not running, even if Fantastic Fan is operating.  FF also serves very well to clear the odor very quickly.  All P-traps are full of water, black tank has sufficient deodorant, dealer has already checked out toilet operation and top vent operation (annoyingly proper).  R-pod forums searched for prior experience with same issue with negative results – guess I’m unique (like everyone else).

Oh, and my black tank sensors lie to me.  Guess you’ve already experienced that.

Time for your best thinking:  what causes this?  Nobel Prize goes to the winner, of course.  Please don’t reply with commiseration or “I have no idea,” because my darling wife has already supplied both of those sentiments.  And, I said the same to her, bless our hearts!

Anybody else out there with AC that pulls a vacuum on the black tank?  Let’s start a new group:  #Sulfurous_Suckers_of_Septic_Smells?  Very alliterative, don’t you think?

Humorously and frustratedly yours, Jim