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Old 08-26-2012, 12:18 PM   #1
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Join Date: Aug 2012
Posts: 133
Adjust Black Tank Sensor??

How do I adjust a black tank sensor that always shows 1/3 full even when empty???
This is for a 247flr open range TT
Also if I can not adjust it how do I know when tank is full,I hope it will not overflow anywhere if it becomes over full.??

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Old 08-26-2012, 12:36 PM   #2
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Join Date: Nov 2011
Location: Hanover, PA
Posts: 589
My tank sensor reads empty right after emptying and rinsing.
Then once I pour a gallon of water and detergent in...2/3 full. UGH.

I have resorted to a flashlight and visible inspection now. Heck with the sensors.

2015 Thor ACE EVO30.1

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Old 08-26-2012, 12:43 PM   #3
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We can tell by the flush sound how full the tank is. We normally wait until the pot "burps" and then dump. The only problem with that is you do not want that to happen when it is driving rain outside and midnite. Tank can be dumped anytime it is 2/3 full or more so we just dump when we hear it is getting full.
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Old 08-29-2012, 03:00 PM   #4
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Join Date: May 2012
Location: Lorton, VA
Posts: 36
Most likely your sensor can't be adjusted. On TT black tanks the sensor is usually a bolt screwed into the tank and it has a wire attached to it. When the moisture level reaches the bolt the liquid closes the loop and the light on the monitor will turn on. What's happening is crud has coated the bolt, or the sides of the tank close to it, and this is giving a false reading. There are a couple of things you can try to clean the sensor.

One is a wand type tank sprayer you stick down the toilet. It works OK but you will have to drag a hose into the TT or through a window.

Another type is a black tank flush, an in the tank rinser, like the Tornado. This is mounted into the side of the black tank. A hose is attached and controlled from outside the TT and it sprays down the inside of the tank.

Another option is the Horst Miracle Probes. They replace your stock sensors. These are designed to not allow crud to get hung up on them. They get excellent reviews.

You can try the Geo Method. This involves hot water, Calgon, dishwashing soap and going for a drive. It's designed to clean the tank and make the tank walls slick so crud doesn't stick. I used this a few times on my TT and you wouldn't believe the stuff that came out. It was blacker than ink.

Another option is to add a few gallons of water and 20 lbs. of ice and go for a drive. The ice will scrub the tank clean.

The last option, and I don't recommend it, is to wait until you get poked in the butt by the brown pyramid. Then you'll know it's time to dump. Looking down the hole with a flashlight when you flush will also tell you.

This is a common problem. Just Google "black tank sensor problem" and you'll get more info to read than you have time for.
Christopher & Michele
2012 Tiffin Allegro 36LA
Northern Virginia
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Old 08-29-2012, 07:51 PM   #5
Join Date: May 2012
Posts: 58
This seems to be a common problem. Mine says 1/3 full after I dump it. I have a farm in the middle of nowhere and fertilize when/where I want but it is annoying.

I ran a hose and filled it, flushed it. Same old "crap." 1/3 full.

Use a flash light to check it.

Last time, used a coat hanger and run it up from the outside into the toilet. Nothing much came out. Not for the faint of heart unless you grew up like me, cleaning out the cow barn as part of my chores.

Some one said that toilet paper/"stuff" gets stuck on the sensors and create a false read.

Not the worst prbblem you can have, just annoying.

They should have a flush counter, letting you know when to "dump."

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Old 08-30-2012, 10:49 AM   #6
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Location: Phx, Arid~zona
Posts: 11,107
My black showed 2/3 all the time. I traced it to the quad comparator IC on the display board. Don't know where I got it, but I had one in my spare electronic part bin. You can also get replacement display circuit boards.

2004 32' National Sea Breeze 1311 Class A on a F-53 Chassis, CHF, TST TPMS, 5Star Tune.
If Dunner (RVM23) can't fix it, it ain't broke!
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