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Old 10-10-2015, 06:16 PM   #1
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Trouble with black tank reading on info center

Need help with black tank sensor, showing full and it isn't. Just got back from 10 day trip to New Mexico and couldn't get the black tank to empty. Got home and husband got it to dump, but the info center is still showing that it is full. Has anybody had this happen and how did you fix it?
Thanks in advance.
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Old 10-10-2015, 06:23 PM   #2
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iblack tanks with sensors on the inside are notorius for inaccurate readings. you have to judge how often to dump. we have externally mounted sensors but we generally dump once per week. but there's just the two of us and its a large tank. just be sure to use lots of water when flushing.
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Old 10-10-2015, 06:29 PM   #3
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All to common. Best, ignore it. I find that with the two ofmus dumping once a week is about right.
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Old 10-10-2015, 07:37 PM   #4
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This question is very common and some folks may not want to repost again. Use the search feature to find hundreds of solutions. The attached picture should help you use search function.

My favorite solution was to install another in tank sprayer that covers the sensors. It may take a few seconds for the sensors to dry out but my black tank sensors are working fine now. I have not had an issue with the gray tanks and don't have a sprayer in it.
Attached Files
File Type: pdf Tank Sensors.pdf (13.7 KB, 64 views)
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Old 10-10-2015, 08:05 PM   #5
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When mine get messed up I add a cup of dish soap and fill with hot water (my 1/2 bath sink flows into black tank). Then, I wait 30 minutes, drain, and repeat as necessary.

I have to do this about every other month. As a fulltimer I expect this more than a weekender might.
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Old 10-10-2015, 09:29 PM   #6
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Thank you everyone, I think we will try the warm water and calgon and see if that will work. I don't know if the 33 degree temp in Flagstaff (burr) had anything to do with the problem but it sounds more like the paper issue.
Thank you again everyone!

P.S. I think we may have an in tank sprayer but we don't know how to use it.
Any help or pics on that would be appreciated.
2002 Winnebago Adventurer 32V
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Old 10-11-2015, 07:39 AM   #7
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As mentioned this is a common problem. The style sensors used in these motorhomes have a tendency to get covered with gunk and give false readings. We had a 2001 Adventurer 32V for over 12 years. Several times both the black and grey sensors gave inaccurate readings. It may be an inconvenience but there are other ways to be sure they are empty.

Fortunately in your particular motorhome the black tank reading can be verified by just looking down the toilet. When the tank nears the full level you can see the water level in the pipe below the toilet.

Over the years there have been many cleaning methods forwarded. Some work and others don't. We used a cup of Pine sol in each tank on several occasions and it seemed to work.

If you can't get the sensors clean they are easy and inexpensive to replace. It just so happens on your model all the grey and black tank sensors can be accessed from the water bay. The front tank is the grey tank and the rear is the black. If you need to replace them this is what they look like.

This link is for informational purposes only. Yesterday I Googled the same link for another post and the price was $7.16.

Here's a link to the previous thread. My post (#4) details how to replace the sensors.

As mentioned earlier yours are easily accessible from the water bay.
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Old 10-11-2015, 08:02 AM   #8
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OK, my lights on the one panel do not light at all only for the black tank sensor, they light up for the others.
I looked behind the panel for any loose wires or something but did not see any thing out of order.
Any ideas?
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Old 10-11-2015, 08:14 AM   #9
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Originally Posted by bobpie View Post
OK, my lights on the one panel do not light at all only for the black tank sensor, they light up for the others.
I looked behind the panel for any loose wires or something but did not see any thing out of order.
Any ideas?
The Suncruiser 32V is identical to the Adventurer 32V. If you open the water bay door you should be able to see the black and grey tank sensors and the probes. Each probe should have a wire going to it.

This style sensor works by using the water in the tank to complete the ground circuit. As the tank fills the probes are grounded and the lights come on. To be sure you have power to the sensors you can make a long jumper wire with an alligator clip on each end. Clip one end to the sensor and the other end to a known good ground. If there is power to the sensor it should turn on the light when you ground the jumper. If the light does come on it's time to replace the sensors.

As a side note these sensors fail both open and closed. In some cases they get covered with gunk that acts to ground them thus turning on the light. In other cases whatever they get covered with acts s an insulation and they won't ground even when they are covered with water.
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Old 10-11-2015, 08:39 AM   #10
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Our coach is a 1989 model, so you can imagine how "gunked" up the sensors were! (we are the fourth owner)
I ended up putting 1/2 bottle of the cheap Dawn dishwashing soap from a Dollar Tree store ($1), 1/2 cup Calgon, and 5 gallons of water before leaving home (each and every trip). The sloshing around while traveling has cleared up all the sensors, and yes, we do have an intank sprayer and I use it each and every dump.
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Old 10-11-2015, 09:04 AM   #11
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We also have the in tank sprayer but I find one of these wands works better Valterra A01-0184VP Master Blaster Tank Wand: Automotive

It is kind of a PIA to drag the garden hose in through the bath window but if you have the bay door open in day light you can see how cruddy the bottom of the tank is and watch the wand clean it. Sometimes the sensors takes day or so to work and sometimes they don't work at all until the next cleaning. It's one of those "got to be a better way" things.

If you are using the San T flush in the tank sprayer, make sure to leave the valve open while flushing. Forgetting it is flushing with it closed can make for an overflow.
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Old 10-16-2015, 06:25 PM   #12
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Old 10-19-2015, 12:54 PM   #13
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I have a sprayer that I put down the toilet and spray clean the inside of the tank where the sensors are mounted.

The wand that works the best has only one spray hole. See the link provided by HD4Mark.

The first time cleaning my sensors I had my wife press the button that illuminated the tank lights. I moved my sprayer until the top light illuminated. I took note of the direction of the spray. Now I can spray directly on my sensors.

Sometimes I have to clean sensors after every dump and sometimes I can dump 10 times before a cleaning is needed. I clean when the black tank shows that it isn't empty.

I spray at the sensors until I get the sensors to indicate an empty tank. I also use laundry toss in soap and Calgon to extend time between cleaning.

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