Waste vacuum pump

It was exactly where Chuck said.

No pump running. Found the pump. Tank is empty. I think it might be the circuit breaker. Wish I knew how to post a picture.

If it stays red but you don't hear the pump running, the black tank is full.

If it stays red and you hear the pump running, its either a cracked bellows or a vacuum leak. Chances are, a cracked bellows.

The vacuum pump is located in the same bay as the fresh water tank, pretty much directly below the kitchen cabinet. You access it through the basement door that contains the outdoor stereo. wa8yxm is correct, if the tank is full you will not get a green light.

The controller and all the electrioncs are the panel the push button is on (Save perhaps for a relay near the motor) The sensors are in the black tank. IT is telling you the tank is full DO NOT FLUSH.> Wish mine did that but alas.. THey did not put the sensors in.

look under the bed toward the back wall? thing about things like this is RV mfg's never build two of them the same way. that can make the hunt a challenge.

otherwise follow the outflow tubing from the fresh water tank?

oops, just realized yours is a vacuum flush toilet. we're simple gravity flush. I did find this page with general plumbing diagram that you prolly already found.

https://www.marinesan.com/VacuFlush-Parts-and-VacuFlush-systems-s/33.htm

it's a start anyway.