black and grey water tank level indicators

rvlarry · 03-11-2021, 02:00 PM

We have a 2010 Winnebago Adventurer35P and have been fighting the tank level indicator problem for a while. We changed out the grey water sensor string which did not fix the problem Both indicators show 3/4 full even when the tanks are empty and do show full a some point. Does anyone know the electronic functioning of the sensors. Do the sensors add resistance when they sense liquid or what? Amy help would be appreciated.

RVwithDogs · 03-11-2021, 02:44 PM

Its my understanding,(I may be wrong) when the sensors are inside the tanks, they are just low voltage contacts. As the liquid rises and touches the contact it creates a ground and completes the circuit to the indicator lamp. Any build up of crud on any of the sensors could then create a ground even with no liquid in the tank.

RVwithDogs · 03-11-2021, 02:56 PM

well after some google stuff, I do see some wiring diagrams showing resistors between each sensor, https://rv52.com/rv-basics-black-wat...m-information/ has a good description.

rvlarry · 03-11-2021, 03:36 PM

Our sensors on the 35P do not penetrate the tank wall. They stick on the outside of the tank. So i think the problem is electrical not gunk but I could be wrong,

Morich · 03-11-2021, 04:08 PM

There are a number of different systems, from the older styles which do have internal probes which are easy to foul to the newer which have pads stuck to the outside of the tank. So step one is to determine which you have.
It sounds like you have the pads, so the solution is different than working to clear debris stuck to probes---since you don't have probes!

This is an area that I've discussed with folks who had false readings but found little for me to recommend as it is not a simple resistance reading but deals for far more "magic" type electronics and I did not stay in the talk long enough to get a good idea of how they actually worked, as the poster found in talking to Winnebago that there was a different board involved at their readout panel and changing that board solved their problem.
Vague memory is that there is a red board and a green and one better than the other, but I'm unsure which way they went to change/fix their readings.
A search of this forum "might" turn up the discussion, sorry that is all I remember but I will do a look back at my posts and see if it shows up.

EDIT:
Maybe some help to start here?
https://www.winnebago.com/Files/File...ire_152594.pdf

FlyingBiskit · 03-12-2021, 05:17 AM

If your sensors are external to the tank they likely use capacitance to measure. The dielectric constant of fluids in the tank is higher than air. You would then have a control board to process the signals from the capacitive pads. If you have replaced the sensors it could be that there is a calibration process needed to pair the sensors to the board or you could have a bad controller.

Morich · 03-12-2021, 08:31 AM

Quote:

Originally Posted by FlyingBiskit

If your sensors are external to the tank they likely use capacitance to measure. The dielectric constant of fluids in the tank is higher than air. You would then have a control board to process the signals from the capacitive pads. If you have replaced the sensors it could be that there is a calibration process needed to pair the sensors to the board or you could have a bad controller.

This is what I meant but could not remember if it was cap or other means, just not a simple contact closure! The poster I was swapping info with DID understand capacitance and we did kind of agree it was out of our range to repair but when they called Winnebago, they got very good service and a board change that fixed their problem of reading 2/3 full all the time.

Sometimes we may be too slow to call the right folks but it is free, so maybe a good idea?

golden13 · 03-17-2021, 05:04 PM

Quote:

Originally Posted by rvlarry

We have a 2010 Winnebago Adventurer35P and have been fighting the tank level indicator problem for a while. We changed out the grey water sensor string which did not fix the problem Both indicators show 3/4 full even when the tanks are empty and do show full a some point. Does anyone know the electronic functioning of the sensors. Do the sensors add resistance when they sense liquid or what? Amy help would be appreciated.

Theoretically, each sensor just completes a circuit when it gets wet or fouled, and they are each placed somewhat higher on the vertically installed tank. So as the level goes up, it triggers another sensor.
UNTIL they all become fouled with caked on TP, and grease in the grey tanks, and start telling you that all your tanks are full at all times.

That's what we seasoned RV'ers have simply resigned ourselves to. None of us bother with the sensors any more, except the fresh water tank. Just empty your black and grey tanks until the water runs clear, and Bob's your uncle!

Morich · 03-17-2021, 06:04 PM

Quote:

Originally Posted by golden13

Theoretically, each sensor just completes a circuit when it gets wet or fouled, and they are each placed somewhat higher on the vertically installed tank. So as the level goes up, it triggers another sensor.
UNTIL they all become fouled with caked on TP, and grease in the grey tanks, and start telling you that all your tanks are full at all times.

That's what we seasoned RV'ers have simply resigned ourselves to. None of us bother with the sensors any more, except the fresh water tank. Just empty your black and grey tanks until the water runs clear, and Bob's your uncle!

If they are correct and they have the pads with no probes inside the tank, this is no longer true as the newer sensors do not have internal parts to foul.

imnprsd · 03-17-2021, 09:10 PM

There are several threads on this subject and no one has yet posted how they fixed their older green Monitor circuit board.

I have been posting a lot of new information on this thread about Testing Tank Sensors:
https://www.winnieowners.com/forums/...rs-360442.html

If you have a "solution" you would like to share, please post it to this thread.

And if you have not yet fixed your holding tank sensor and/or Ventline Monitor Panel circuit board, you might want to subscribe to the above thread.

This subject is still a "work in process," but hopefully this summer, with more eyes on the subject, we will come up with a green or red circuit board fix, because just switching to Horst Miracle Probes is not always a foolproof solution.

plrude · 03-18-2021, 01:35 PM

If your problem might be gunk stuck, use Caravan cleaner found on Amazon. I put it in my tanks with fresh water and let it set for a week to two weeks. The microbes did a fantastic job of cleaning our 15 year old tanks spotless. Unfortunately they ate all the crud around my dump valves that was keeping them from leaking. Anyhow, new valves and clean tanks!

imnprsd · 03-18-2021, 06:57 PM

Plrude: Thanks for the tip!

Here's the Amazon link to Caravan tank cleaner:

https://www.amazon.com/Caravan-overn...6114804&sr=8-1

I read the Amazon reviews on this stuff and most are very positive, much to my surprise.

It also sounds like the longer you leave this stuff in your tank, while the RV is in storage, except during the freezing months, the better.

I didn't read all the reviews, but it sounds like leaving this stuff in for 2-3 months might be a good thing, with one downside... the enzyme cleaner could create a leak in the black and gray water tank drains,

Does it work to break down Struvite too?

What is Struvite? Watch this:

https://www.youtube.com/watch?v=Fsl7ukzkXEI