10 replies to this topic

[joealackness]

My sensors read full on my gray tank. I was at a RV dealer and asked about replacing the sensors. They had new sensor for $.65 each. (The old ones were glue in and could not be removed.) I replace them and the tank still reads full. How does the system work electrically? I would think that there is a positive to the system and the sensors are ground.

Joe Alackness
2008 Forrest River Charleston

[GaryH17754]

You could try inserting the new sensor in a glass of water which is the ground for the circuit. A dry sensor should give a NO LIght reading. When water touches the sensor, the light goes on. If the light comes on with a dry sensor, you have a ground somewhere else causing the light to come on.

[wolfe10]

Contact the maker of the monitor system-- no need to guess how it works.

[RVerOnTheMove]

The general theory behind any sensor where some part of the sensor enters the tank itself is that the bottom most sensor would not provide any reading (empty) until the water level rises enough to touch the probe above creating a circuit. When the water level creates a circuit between the bottom (ground or power) sensor and the one directly above your gauge would read 1/4 (or lowest option). As the water rises and touches the 2nd sensor the 1/4 and the 1/2 lights would be lit followed by 1/4, 1/2, 3/4 and the 1/4, 1/2, 3/4 and Full.

[desertdeals69]

After fighting in tank sensors for some 25 years I installed SeeLevel system which has the sensor strip on the outside of the tank. Very accurate and give levels in percentages.

[mrboyer]

I have installed SeaLevel sensors in three coaches. These are the only ones that have worked well. Digital display reads 6% increments.

[Steve4x4SolarElectric]

I had the same problem in every RV so far with the pin type sensors. I looked at Quartzsite and Indio rally for a better sensor and found none. So later I bought an inductive sensor like SeeLevel, which senses the liquid level by signal sent thru foil tape on outside of the tank. The more liquid is in the tank, more signal is picked up from one foil strip and passed on to the other foil strip through the liquid. Both on outside of tank, so there is no deterioration or contamination from the tank contents, and no drilling the tank required.

Actually I ended up with a different brand that was in stock at Camping World. It works great, solving the problem forever. One unexpected difficulty was that the new unit needed 3 wires from the tank whereas original had only two each tank, so I did have to run a new cable to each of the three tanks.

[desertdeals69]

I think when I installed my See Level system it required 2 wires and I had 4 or 5 wires with the original system, been quite a few years ago since I did it. Has worked well all these years.

[ClayL]

The problem is that fluid holding crud builds up on the tank walls and that fools the sensors into thinking there is fluid in the tank.

If it's made by Ventline as many are, there is a 68k ohm resistor between the full and 2/3 sensor and one from the 2/3 sensor to the 1/3 sensor. The wire from the panel connects to the full sensor. On some units the resistors are potted in a small plastic cup close by the tank with one wire leading from it back to the panel. There is another wire from the ground sensor also going back to the panel. There are also wires from the cup to the sensors.

On others all four wires go into the wiring harness and I don't know where the resistors are located. Maybe on the display panel?

The display panel has five "LM339 Low Power Low Offset Voltage Quad Comparator" ICs (one for each waste tank, one for the propane tank, the water tank and one for the battery voltage) that are used to sense the voltage drops across the sensors and activate the proper LED.


The non-contact sensors are better but not foolproof either. According to their web site the SeeLevel system can also be fooled but at least it just stops giving a reading rather than showing a false one. That is your signal to clean the tank walls.

I have the TrueLevel non-contact system that Winnebago went standard with in 2005 (right after I bought mine of course so I had to add it) and right now my black tank reads full all the time but the top two LEDS of my gray level are accurate.

I have pressure washed the black tank wall twice and it worked okay for a while then started reading full all the time.
In my years of trying all of the things people recommend I have not found anything that keeps the tank walls clean enough.

Some people have reported that the HORST MIRACLE PROBES work well. They shield and move the sensors out from the tank walls so the gunk doesn't fool them.

[JimM68]

I think when I installed my See Level system it required 2 wires and I had 4 or 5 wires with the original system, been quite a few years ago since I did it. Has worked well all these years.

Ditto. seelevel rocks. and (if you put a second monitor in the water bay) only needs 1 wire going topside.