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Old 10-29-2012, 02:25 PM   #1
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Black Water Sensor

I have a cc magna with the silverleaf total coach control. The black water shows to be 50% on the tank capacity, but that is not correct. I have washed, flushed and backwashed but it still shows this reading. I am sure the tank is clean. It has a backwash port on it and I even built a pressure washing wand and inserted it through the head and washed thoroughly with soap and water. The sensors are on the outside of the tank and they are all still glued on and wired. I did all the above and then filled it half to three forths full , added laundry soap and drove it about 200 miles (without using the facilities) then dumped , washed etc. and it's still reading the same. Has anyone had this before and how did you fix it?

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Old 10-29-2012, 02:30 PM   #2
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No matter how much we clean and flush,the sensors usually give out false readings. Could be buildup that you cannot reach or just a bad sensor. You will have to gauge your use and empty periodicaly. I knew mine was empty so I kept up with the gauge and found a medium level to go by

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Old 10-29-2012, 04:25 PM   #3
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Fill the black tank abot 1/3 full, pour in a bag of ice cubes, then drive the coach around for an hour or so. The ice cubes will clean the gunk off the sensors, after you drain the tank, the reading should be correct unless you have a bad sensor.
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Old 10-29-2012, 04:45 PM   #4
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Originally Posted by jlfbatonrg View Post
Fill the black tank abot 1/3 full, pour in a bag of ice cubes, then drive the coach around for an hour or so. The ice cubes will clean the gunk off the sensors, after you drain the tank, the reading should be correct unless you have a bad sensor.
this except I add Pine Sol- the whole quart jug and it really cleans the walls of the tank some say Dawn but I use PineSol with good results .
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Old 10-29-2012, 04:56 PM   #5
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Simple fix without the washing, etc. but do keep your tank clean.
Model 709 SeeLeveL II
available many places other than above and they use external sensor rather than internal...fixed my problem in a 1 hour install, very simple. Plus you can have a panel inside and in your drainage bay/area.
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Old 10-29-2012, 04:56 PM   #6
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Ice will work most times, Pinesol or Dawn or dishwasher soap work most of the time. Laundry detergent with Calgon wetter is my favorite. The fact is, however, that sooner or later, most of the time sooner, the sensors will get fouled again and not show the right level. Most of us who travel a lot ignore the sensors and use our ears for the sound of a nearly full tank, or look inside with a flashlight. Some spend the money and use external sensors that work much better.

If you do a search of the forum, you will see a lot of questions on this same subject. Unfortunately, there is no real good answer to your question.
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Old 10-30-2012, 09:57 AM   #7
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My fresh water and black sensors are incorrect. I just talked to my RV mechanic of 35 years and he said to put 2 talbespoons of salt or baking soda in the fresh water tank. Put much more in the toilet, sink drains and shower drain. Then, drive around for awhile. He said the electrodes on the sending units get corroded. Salt seem to work best. I'm going to try it on mine today.
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Old 10-30-2012, 01:02 PM   #8
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Or do what most of us do and learn what the 'burp' means - that's when you dump. It really should only take a week or two for anyone to learn your usage pattern and when it will be time to dump. Or you can spend a lot of time and money worrying about it.

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Old 10-30-2012, 01:09 PM   #9
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You take 20 or 30 gallons of water and dump a bag or tow of ice, you had better do your driving pretty quickly as the ice will melt pretty quickly and all you are doing is sloshing wcold water. One other issue with the ice and getting the tank too cold...most of the plastics used in waste tanks getss pretty brittle when cold...so more ice may not be the answer.

Waste tank sensor do not work as they use the cheapest technology possible. The manufacturers could upgrade a bit and get sometihng that will work...but the accountants say that it is good enough to get them out of warranty and they look at the bottom line.

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Old 10-30-2012, 05:08 PM   #10
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I have cleaned the inside by filling half way and adding plenty of soap, tried again with pinesoil and did it a third time with tide washing liquid. Drove 200 miles with the latter, flushed good with fresh water several times and still shows 50%. The sensors are external. Maybe a bad sensor.
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Old 10-30-2012, 05:58 PM   #11
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Did you say the sensors were on the outside? Mine are and I got bad readings as well. Even when it was new. Took it back to the factory and they determined the sensors were located in the wrong spot.
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Old 10-30-2012, 06:11 PM   #12
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Never ending story for us all. Most likely a bad sensor since it is external! No matter internal almost never work. We have a new coach and the black side only works intermittently despite using every trick mentioned above. Live with it. You will learn when the tank is approx. half to two thirds. Just keep plenty of water flushed ALL the time. Use a good enzyme.
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Old 10-31-2012, 03:06 PM   #13
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Yes the sensors are on the outside. I know it is not a big issue as we know just about how long to go before we need to dump. However it works some of the time showing O % but when it does malfunction it affects the control panel. It will show a problem and the amber lights come on and the green led lights blink constantly giving the silverleaf a false indication that something is wrong. I guess I need to change the sensor or just overlook it.

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