monitor panel black tank display

I know many don't care if the idiot lights on their monitor panel work or not... I do because I am slow!  My monitor panel appears to work just fine for the two gray water tanks, fresh water tank, water heater and water pump. The only issue is the black water lights are all kit. I cleaned the black tank pretty well and then installed NEW Horst Miracle Probes; all the wires from the probes look fine. All the lights on the monitor panel are still lit. I am not sure how this system works but the probes provide ground I am sure when water reaches them and since there is no water reaching them, where could the ground be occurring? The probe wires all go to a red thing and I suspect the hot wire is just inside the monitor.

Any help on how to trouble shoot this issue would be appreciated! TIA wg

Slime and other waste can build up on the tank walls and essentially shorts the probes together. The Horst probes are supposed to reduce that problem, but they are by no means perfect.  And if the top probe is grounded, the gauge shows full no matter what.  Can you disconnect the wire to each probe to determine which, if any, is always reading?  If they are all disconnected and the gauge still reads full, you know the probes are ok and the problem is at the board or the wiring in between.

The Horst probes are supposed to be immune to the build up.> May be an error in hookup.
(This is the first I've heard a negative on Horst Probes)

Try this, Label and remove all of the probe wires save the bottom one (That's ground) check the lights, Should show empty. if not you hooked 'em up wrong or there is a short or open somewhere (Open ground on the display)

For the rest of this I will assume your display shows 1/3 2/3 Full
If it's a 1/4 1/2 3/4 Full I will leave it to you to figure out the obvious adjustment

Then one at a time, using a clip lead, hook one of the wires to the common wire (The bottom or ground) if the lights now show 1/3  Hook that wire to the next sensor up
2/3 the sensor above it, FULL the top sensor

Then re-check to see if it again shows EMPTY.. IF so pick another wire and repeat till you have all 4 wires connected.

Good luck on getting the OEM probes to work.  Tried all the tricks I could find, dawn, Calgon, ice cubes, bumpy roads, lots of starts and stops, miracle tank washes.  After 3 months of that last spring I called it quits and bought a Seelevel system https://amzn.to/2GGw4an.  One year and 14k miles later, its the best $200 I spent on the coach.  It just works!  -Bill

I've got the same problem,  only it's the gray tank. My sensors are externally mounted.  In the past,  I've had some success by filling the gray tank for about 10 minutes, and then adding mixture of 1/4 cup of Dawn and 1/4 cup of Calgon water softener mixed in a gallon of water. (Tip: put the Dawn in last before shaking the bottle. )  Then drive to your next destination.  I'm traveling again this Tuesday so I have to wait until then to try it. f

Folks, installed the Horst Miracle probes so they are NOT covered with anything.  Promise.  The tank is empty (you can figure that out when you remove the old probes; if not empty you will soon find out hehe.  After install, contacted the RVPROBES.com and asked for some tech help.  Here is their response:

Also,here are some steps that might help you find the issue, and help determine if it could be the monitor.

    1-  Disconnect all wires from the tank and measure resistances in Ohms between the common (white) and the three level probes with no water in the tanks. It should read infinity on the Ohm meter

    2- Measure the resistance between the wires while they are disconnected from the probes.
    Between green and yellow should be about 120000 ohms
    Between orange and green should be about 68000 ohms
    Between orange and yellow should be about 188000 ohms

    Typically the resistance between the common probe and any of the individual probes while submerged and with no wires on them should be about 10000 ohms to 100000 ohms depending on the water.  This must be done with an analog ohm meter.

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I then crawled under my 5ver, removed the wire leads to the probes and performed all the resistance checks.  All tested exactly as they should.  The RVPROBES folks believe the monitor panel is the issue.  I have a panel manufactured by KIB.  I found an exact replacement from https://pdxrvwholesale.com/ - The new monitor panel was $37 plus shipping and it is on the way.  Will follow up when it arrives.  Hopefully the fault finding procedure isolated the issue to the panel.