My holding tank monitor system will light up when you push the button/switch for either the gray or black water tank BUT it give a false reading. It shows black water tank as being half full when it is actually empty and gray tank as being about 1/3 full.
Does anyone know how this system works ? I look under the trailer and see several wires screwed to the side of each tank. Apparently it is hooked up but giving me wrong readings.

I have owned two HiLo's and both of them gave inacurate readings. On the 1996 DH consulted with the service advisor about running a new ground wire. When you crawl under you will see four wires. The first wire you see is the ground wire. Run a new ground wire. Our only inacurate reading is the black tank. New Horbst probes cost $250.00. Not worth it to me. Mostly do 2 or 3 days of camping. We have never overflowed any of the tanks. On our six day campout we empty with a blue boy after 3to4 days. We use the campground showers. Your tap will sputter when you are out of fresh water. I have read where most manufactures use faulty/inaccurate tank monitors.

I'm sure your tank probes are coated with an electrically conducting "slime" that gives the inaccurate false reading. My tank monitor did the same until I changed the probes to the Horst Miracle Probe brand. I suspect the cost sam posted included installation, but I installed them myself. It's not too hard.

You can buy a set for each tank on Amazon for less than $30 each. Here's a link: https://www.amazon.com/Valterra-T213.../dp/B00YJIB7WE As you will notice, there is a different design between the two tank types. The black water tank probes have a cover over the probe wire that prevents toilet paper from touching the wire. The grey water tanks have no cover. The probes are long and there is a long insulating part that prevents the conductive problem.

It is possible you may find the probes even cheaper. As I recall, I bought mine from etrailer.com.

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System, SoftStartRV mounted on A/C
2024 F150 Platinum FX4 3.5L PowerBoost SCrew

My apologies on the incorrect price for the probes. Must have looked up some other rv part. You can order from Rec Pro for 4 probes at $22.95 plus free shipping. 5% off first order. Hm!! might be able to talk DH into installing these. Today he finished a major cabinet modification to install a new radio and antenna. The old radio was from 1996 and had lost one channel. Speakers were upgraded. Will get some pictures and post soon. When we changed out the toilet to an ADA one the paneling that covered the baseboard no longer fit. The paneling is no longer available. So he had to do a fab job out of the scraps.

No apologies needed sam - we all appreciate your participation here and thanks for letting Freddie know about the less expensive source.

- Jack

Thanks for the help on this one. I had no idea how this thing worked. I was thinking something like floats. Got back under camper and now realize what the black rubber under each wire and screw is a seal for the individual sensor probe. I got on the computer and found the ones on Amazon to see what they looked like. Will probably order some today. We just took a short trip to a Texas state park that had only electric and water hookups and a dump station on your way out. Makes me nervous not being able to know where my tank levels are. Especially the gray water tank which in the past seemed to fill up really quick. This trip we used a plastic pan to catch the water in the sinks and then used it to refresh the commode water level each time we flushed. Thank all of you, again. We are leaving out shortly on a 9 day trip to the coast but they do have sewer hookup.

My grey water reading never changes from E. When the tank is over full, shower/tub doesn’t drain. Time to drain or partial drain the tank depending on when we’ll be leaving camp.
John

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Jonboy
2022 Venture Sonic Lite 27 ft. 2007 Navigator
Previous 2006 25 ft Classic, and 1999 26 ft Classic

jon - check the wiring to your monitor panel from the probes. I suspect at least one of them is disconnected, or, the connections are bad.

- Jack

clean your tanks helps a lot. I bought a wand that has a rotating or spinning head on it when water is hook up. you stick it in the toilet and the water spins and cleans the side of the tank. Had to do it about three times before my black water sensor was accurate. as for the grey water, no clue unless you can find an access to do the same.

I use that spinning wand cleaner too. I think, however, that the OEM sensors just develop a conducting film on them that eventually causes them to register incorrectly.

- Jack

After checking the ones at Amazon I looked under my camper again and I have 5 wires on the side of each tank and the sensors come 4 to the order. What is the deal ? I am assuming that on my tanks there must be one each for empty, 1/4 full, 1/2 full, 3/4 full and full. Am I looking at the wrong set online ? My camper is a 1990 model ( 229L ). And we are on our 3rd day out and setting on the Gulf Coast in blowing rain and cold today. Should go back to warm tomorrow. Have been trying the soap thing in tanks but no change so far. Sure I will tackle the new sensor thing when I get back.

Freddie, I believe the 5th wire is the common wire (possibly the ground) for each of the sensors. I THINK the monitor shows "Empty", 1/3, 2/3 and full and the 4 sensors are for those positions.

- Jack

My tanks only have four probes on each tank. One is common and the remaining three are for 1/3, 2/3, and full.
Beach

Like Beach says, my tanks use only 4 probes too. I don't recall any 5th wire to the tanks either, but it was several years ago that I changed the probes and maybe my memory is not too clear.

Freddie - can you see if one of the connections at the tank (probably the one at the bottom) looks different from the others? If so, it's not a probe but just a common circuit. Regardless, even if it IS a probe at the bottom, it will not cause an incorrect reading if not changed. The ones that cause problems from the conductive coating are the upper ones.

When you take the old probes out, you'll be able to see why they become easily faulty, compared with the superior design of the Horst probes.

- Jack

Ordered Horst Miracle Probe sensors for black and gray water tanks from Amazon for $ 58. total for both tanks. Very easy to install and got correct readings from both tanks as I filled them with water. Wish I had done this two years ago. Staying in some of the Texas state parks that do not have sewer hookups made me nervous without these tank readings. Thanks again. Taking a two night trip in about 10 more days and will get to see how it is knowing where I stand on my tank capacities. Sure I will be more at ease.

Cool! Glad you had a successful installation! I've been pleased with mine too.

- Jack

P.S. # You were right about the fifth wire ( at bottom ). It is a WHITE WIRE AND APPARENTLY IS THE GROUND WIRE. The top four wires gave me 1/4 , 1/2, 3/4 and full.

Whew! Another win! Half the time I wonder if I have any brain cells left!

- Jack