I had been plagued with false sensor readings on my holding tanks for many years. I have tried many ways and techniques to eliminate this problem with no good permanent results. I have found the answer - Horst Miracle Probes.
I now have 3 camping trips under my belt with these sensors and am still getting correct readings with them. They use teflon in their construction and stick out further in the tanks than the standard type sensors. Once I figured out my method of attack in removing the old and installing the new, it was quite simple. The sensors for the black water tank are designed different than the sensors for the grey water tank. There are four sensors in each kit. They cost $62.95 plus shipping for the two sets. Money well spent. I have four more trips planned thru October and will update on how the sensors function. For now I am one happy camper!

We purchased a new 1508T last year at a wonderful price, but for whatever reason HI-LO decided not to put any tank sensors in the 15'. They probably wanted to keep the cost down, but 15's were pretty pricey anyway. Lucky for us, when I investigated putting a sensor system in, I stumbled on the SEELEVEL gauges at RVGauge.COM. These sensors eliminate the problems that in-tank sensors have by adhering an electronic strip to the outside of the tank that senses liquid level exactly ! A kit cost about $171, and does all three tanks as well as internal / external temperature and optionally LP tanks. Anyone plagued with in-tank sensor problems and is a little handy, can just switch to the external sensors / central monitoring station, and use the same wiring. You can just leave the in-tank sensors -- just move one of the wires over to the sensor strip.

Jeff

retiredcamper47

Can you provide just a brief description of your method of attack. I am interested in replacing my sensors as you did but don't have any idea how to get started.

kengsr (another retired camper)

Make sure that both tanks are empty! I backed my trailer onto leveling boards to elevate it to give me some "wiggle room". Tools needed - two 3/8" wrenches, pliers, small crowbar (about 1' long), and a piece of thin wood. I used a scrap piece of laminated flooring. The sensors consist of a machine screw going thru a rubber grommet, a flat washer, and 2 nuts. Take the first nut off to remove the wiring to that sensor. Back off the second nut and washer but leave it on the sensor. The purpose of this nut is to compress the rubber grommet so that it forms a seal to keep the tank from leaking. I had to use the pliers to hold the sensor while backing off the second nut. Otherwise, the whole thing will spin. Place the curved end of the crowbar on the sensor so that the washer is being gripped. Place the board under the crowbar at the pivot point to distribute the "force" on the tank. Using 2 or 3 gentle rocking motions on the crowbar, I was able to pop the whole unit out, grommet and all. Unfortunately, I could not use the crowbar on the very top sensor of both tanks. My HiLo is a 2001 29' and the tanks are mounted midship. There was a brace coming off the frame that wouldn't allow me to use the crowbar on the top sensors. I removed the second nut and washer and just pushed the sensor and grommet into the tank. Hated to do it that way but had no choice. After doing the grey water tank first, I checked the monitor panel to make sure I had a reading and that the correct tank matched up to the proper switch on the panel. This is how I did it. I lucked out and did not crack either of my tanks. The above is for reference only. Anybody replacing their sensors do so at their own risk.

Thanks. Glad I asked. Good to know I don't have to drill more holes. Can't imagine the tanks are very fragile, and our 2306C looks relatively easy to access the sensors on, so I may give it a try

Kengsr

Just a note of support for Jeff on the SeeLevel gauges. I installed them on my 2704. They are digital readout by percentage ( ie 23% full). and I'm happy with them! No drilling! I accessed the fresh water tank by cutting a door with my dremel tool and then reinserting it with metal and pop rivets.
Lloyd