Black water sensor - Is it the sensor, the ground or the circuit board?

[MurphyMan]

2006 Winnebago Outlook, WF326A . Yet another thread about level indicators?

Symptom: The 2/3 full black water monitoring light is not coming on. However, the Empty light, the 1/3 Full light and the FULL lights appear to be working. The grey water appears to be working.

We have the True Level sensors, which are mounted on the outside of the tank. I spent a lot of time and water, cleaning the inside of the tanks, so I think they're pretty clean. When you touch these type of sensors, the board lights up. So to help troubleshoot this, I went under the RV and placed my hand on the sensor while my wife observed the lights inside.

I also took a look at the circuit board. According to what I have read, the current level is a red board, we have a green one. The P.N. is L5131-02.

Checking the voltages at the connector we get:
Black water (empty) = 5.05V
Grey water (empty) = 5.05V
Fresh water (full) = 4.66V

So, anyone have any experience troubleshooting this? Also, how do I find the chassis ground connection? I think I ought to make sure that it's nice and clean.

A new board is $75 and I may order one out of desperation but I hate throwing parts at a problem without knowing the exact cause.

Thanks.

[Morich]

Good deal on not swapping parts until you know and it is quite likely not needed-- but you do need to test!
Some starter info here:
http://www.winnebagoind.com/diagram/...ire_152594.pdf
This is the drawing for the sensors and needs some info, depending if you have one or two monitor panels on your RV. Sheet 1 of 2 has tow drawings much alike but there are option triangles on the drawing at the left side showing 1 and 2 or 1 and 3. Those triangles refer to the notes at the bottom left, so step one is to decide which drawing to use and which to ignore!
I often have to compare what I think the drawing is saying to what I actually see but my guess is that these notes let you decide if you have the diode pack and how it is connected on drawing sheet two!??? See options 2 and 3 at the right end of the drawing?
But if you can locate this diode pack, (which may only be a small set of wires with a small bulge?) there is a ground wire labeled "GL". GL is the number two pin on both the 3 wire and 2 wire connectors. I've never seen one of these, so some guessing on the appearance/size/location!
I might want to check continuity on this diode pack, both at the ends and also the diodes themself.
Wire ID chart here:
https://www.winnebagoind.com/diagram...ical_guide.pdf
I'll hold on more info until you see if you can find and access this, but if in doubt how to test or go with the diodes, give a shout and we can get deeper. Not hard to test with a meter but no need to confuse/ bulk up the issue if you can't get to it!!!
Let us know what you find? May only be a crusty connection!

[Morich]

Just setting here doing a close read of the drawings and looking for ground! Always good to know where to which way to ground, huh?
I suspect you have been to this drawing as you seemed to have some info on the board but which of lots of options do you have?
http://www.winnebagoind.com/diagram/...ire_134940.pdf
I did what I "think" is the correct reading of the panel in the top left for choosing which sheets fit for your RV, but does this meet what you find and which sheets seem right for you? Some of their descriptions seemed pretty vague until I studied a bunch more!
First two lines show with gen and no gen but they mean generator hour meter?
Does this look right for you? If it looks right, which sheet (options?) for you?
Maybe click the picture to get a better view if on a PC.
If I'm reading right, it looks like ground comes direct from chassis ground to the monitor on a pin 3 of a 15 pin connector in several of those I looked over.

[MurphyMan]

I contacted Winnebago Customer Support and they sent me these two attached documents. If you look at the bottom of the Mirus document, there is a photo of the styles of sensors. We have the ones on the left.

FYI - We have a generator with an hour meter.

It still doesn't tell me where the ground connection is physically located. The wires just disappear into the wall.

What I don't understand, if the three sensors are in series, why would the 2/3 act up, yet still the FULL light to come on?
I guess I need to do these tests next. I'll poke around and see if I can find a 47Kohm in my junk drawers.

Poor ground at monitor panel or at holding tank ground probe –
Verify ground panel and ground probe with a continuity tester.
Wire to tank resistor harness disconnected or damaged –
Verify wire is connected and free1 of damage. Replace if necessary.
(With the tank resistor harness correctly installed and free from
damage, a jumper wire containing a 47Kohm resistor placed
between the holding tank ground probe and any tank level probe
should cause the respective tank level lights to illuminate.)

Short circuit on circuit-board – If the above test fails to illuminate
the level lights, repeat the test at the monitor panel. Refer to the
wiring diagram for the correct wires to jump together. If lights
illuminate, replace the wiring between the panel and the tank
resistor harness. If lights do not illuminate, replace the circuit
board.

[Morich]

Got you and now some thinking?
If the levels for the fresh and grey all work okay, can't we assume the ground is good to the point I've marked on this snip?
Since the black water 1/3 and full LED light, can't we say the ground is getting to that set of sensors? If you can access that connection where I've put the question mark, I think it pretty sure you will find ground there.
No mention from Winnebago of the diode pack, I thought about? Something skunky with diodes might be my first thought but if you don't have them, bad idea!
So are you getting down to saying a bad LED for 2/3 full? Rare but can happen?
Mt thinking is that the wiring is common for all levels of tank, so I would say the wiring is okay, just because all the rest works?
Your voltage readings look very close to what they spec and sound okay.
The operation of the sensors gets into such low current, I'm not sure I have the right stuff to measure that level. I'm more into testing 15 amp and more, so have never looked at my meter for how low it can get!!
That 2.5ma of current is .0025 amp and I had to go to a conversion chart to even think at that level! I'm not sure but what my sweat makes more current than that, if you know what I mean.
Seems like you have it down to being bad led which you might check if you can get to the back of it, or the sensor pad itself?
Check my thinking before thinking it's true!

[MurphyMan]

I wound up changing the board. The old green one was Rev A and the new red one is Rev C.

In installed it this morning and went under the rig and placed my hand on the sensors.

Everything worked properly!!!

[MurphyMan]

Just to document for any folks in the future, here is the sheet that says to switch to the red circuit board.
https://winnebagoind.com/resources/s...ue%20Level.pdf

[Morich]

Interesting info there with a couple things of special interest.
first is that it says they red board was from 2005 on but you seem to have gotten the green board? Sometimes a guy just doesn't time it right!
But a bigger one going forward may be this little note that can be easy for many of us to miss.
" With non-contact sensors, all metal wires and harnesses must be kept ¼” to ½” away from sensors to prevent interference of sensor operation"
Thinking of where these sensors are located and how we may stuff all kinds of things in the storage compartments, it looks like it might be easy to mess with our minds if we did it wrong. Something like a little set of sockets, stored in the wet bay and right next to the sensor? Wouldn't that be a trick to find and cure?
Every time we pulled the tools out, things worked but when we stored the tools, the sensors stop working! Maybe not a good place to store the can of WD-40 or that old metal funnel you use to add hydraulic fluid?

[imnprsd]

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 so that we can get the message out to everyone.

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.