My sensors did not work when I purchased the my MH used. It is an old MH (1985) and certainly does not have "fancy" sensors. Just the type that many here will tell you wont work. Well, mine work and have ALWAYS worked since I "fixed" them. All I have done is use the GEO method minus the bleach. I only dump when the tanks are full. I NEVER backflush, rinse, etc. Just dump each tank and add some water back to the tanks after I am done dumping. That's it. I use Happy Campers in the black tank (and once in the gray tank).
https://www.5starhappycamper.com/order.html