Holding Tank Sensor Cleaning?

NR4A · 12-07-2006, 12:45 PM

Our black holding tank is now showing 2/3 full when it is empty. The tank is flushed a few times every time it is emptied, but the display still shows 2/3 full.

I know there are many products at CW that should disolve any stubborn solids in the sensors, but Im wondering if any of them work and what people are using?

Had this same problem over the years on the 5er, TT and other motorhomes we've owned.

NR4A · 12-07-2006, 12:45 PM

Our black holding tank is now showing 2/3 full when it is empty. The tank is flushed a few times every time it is emptied, but the display still shows 2/3 full.

I know there are many products at CW that should disolve any stubborn solids in the sensors, but Im wondering if any of them work and what people are using?

Had this same problem over the years on the 5er, TT and other motorhomes we've owned.

tomsm · 12-07-2006, 02:25 PM

Sam - I haven't had the problem yet so I can't verify this technique, but have read that many have good results with dumping a bag of ice cubes down the toilet just before starting the days's drive. The cubes stay solid long enough to scour the inside of the tank while you drive. Worth a try...

NR4A · 12-07-2006, 03:02 PM

Hi Tom -
I've heard of that trick, too. But havent tried
it. Would not take very long to melt ice cubes in the 90 degrees Florida weather. Now that it's getting cooler temps, though - it may be worth a shot.

Someone suggested Citric Acid on another webpage, but Im hesitant trying it not knowing how caustic it is.

LIke I said, I have had this on every one of my RV's over the last 25 years. Theres bound to be a simple cure to it.

JD Allen · 12-07-2006, 04:32 PM

Here is a site that talks about the "Geo Method" of cleaning holding tanks.

Geo Method

John_Canfield · 12-07-2006, 04:57 PM

Sam - do you know if you have the external or internal sensors? Our gray now always indicates 1/3 full but that's not a big deal. Probably our fault because we usually leave the gray valve open when we are parked for a few days.

Harry B · 12-07-2006, 05:21 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Sam - do you know if you have the external or internal sensors? Our gray now always indicates 1/3 full but that's not a big deal. Probably our fault because we usually leave the gray valve open when we are parked for a few days. </div></BLOCKQUOTE>

Interesting John, I have the same coach as you do and have I the same 1/3 full when empty problem on the gray tank.

There are several pots on the back of the indicator panel. I wonder if they are to adjust the sensitivity of the external sensors?

Does anyone know if this is so?

NR4A · 12-07-2006, 05:36 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Sam - do you know if you have the external or internal sensors? Our gray now always indicates 1/3 full but that's not a big deal. Probably our fault because we usually leave the gray valve open when we are parked for a few days. </div></BLOCKQUOTE>

John,
When we looked at the Vectras and Horizons I was under the assumption they were all external but I believe I was wrong. Im 99.999% sure mine are internal on the Horizon.

We stay parked a month at a time with grey water valve open all the time. We read empty on grey. I empty the black tanks usually once a week, then use the tank flusher to fill the tanks 3 or 4 times and empty again. I have a clear plastic adapter and know when the black water is clear - but the indicators are still showing 2/3. They were all at empty when we took delivery. After a month i was starting to show 1/3 when empty. Now im up to 2/3 and its been that way for 3 weeks now.

What are your thoughts on the Citric Acid?

NeilV · 12-07-2006, 06:26 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by NR4A:
What are your thoughts on the Citric Acid? </div></BLOCKQUOTE>

Used by applience service techs to clean out dishwashers. Works well in that application but will turn aluminum black.

Ding-a-ling · 12-07-2006, 06:43 PM

One tip I had read in a WIT Club News tech tips article was to make sure the wires going from sensor to sensor are not wadded together. The wires must be separated so "crosstalk" is not induced between sensors. If you can see them, check it out.

DancinCampers · 12-07-2006, 07:59 PM

I use a tank cleaning procedure outlined by Paul of 3-T's. Works great, my sensors now settle down after about 5 minutes of stopping. Fill tanks 1/2 full of water, add 1/2 cup powder laundry soap to each tank (I used the cheapest I could find at the Dollar store) , drive to destination, empty. Just like a washing machine.

cbeierl · 12-07-2006, 08:05 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by NR4A:
... When we looked at the Vectras and Horizons I was under the assumption they were all external but I believe I was wrong. Im 99.999% sure mine are internal on the Horizon. ... </div></BLOCKQUOTE>
The wiring diagrams for the 2005 Vectra/Horizon models include the following note:
** Units manufactured before 4/30/04 utilize a Direct Contact Tank Level System and have a green circuit board on the monitor panel.
Units manufactured after 4/30/04 utilize a Non-Contact Tank Level System and have a red circuit board on the monitor panel

I don't see such a note on the 2004 wiring diagram, however, so I would assume that the 2004s have the Direct Contact sensors.

NeilV · 12-08-2006, 01:16 AM

My Adventurer gets like that if I don't make use of the tank flusher that came pre-installed on the black tank. I use the bleach and liquid laundry detergent method putting it in the tank before I drive off and then do a thorough flush when I reach my destination. A few taps of the brakes to get things sloshing around helps with the process.

bflem · 12-08-2006, 02:41 AM

A few years ago at GNR Ventline had a seminar on the holding sensors and passed out a booklet with wireing diagrams and explaining how to adjust the pots in the monitor panel. They may send you one if you call them.

RKL2 · 12-08-2006, 05:39 AM

I use Dawn dishwashing liquid detergent about once a month in both tanks..close valve on grey to get gray water above the sensors and let sit overnite.....3 winnebagos and never had a sensor issue doing this.good luck RKL

Clay L · 12-08-2006, 06:31 AM

As cbeierl said the 2005s have the non-contact sensors. The PC board they said is red is really green. Apparently the red was a manufacturing designation of some sort. That confused the Winnebago techs somewhat when they worked on mine.

The only adjustment on my TrueLevel board is for the LP sensor. There are potentiometer holes for the other sensors but on my board they are jumpered with a fixed resistor since they are not useable on the TrueLevel sensors. The TrueLevel sensors are on-off sensors in series. In effect as each one closes, it shorts a resistor (contained in the black sensor square) which changes the voltage level on the pc board and that is what is sensed.

The problems are not due to dirty sensors but actually dirty tank walls. The walls get crudded up with stuff that contains water and fools the direct contact sensors.
If there is enough crud it will fool the non-contact sensors also.

I installed the TrueLevel system at the factory summer before last and the indicators showed the grey and black tanks to be full when they were empty. The Winnebago techs tried everything they knew including replacing sensors and the pc board to get it to work but couldn't.

After leaving the grey tank valve open all summer, it has started functioning at the 2/3 and full positions.
This fall I pressured washed the black tank by putting a pressure wand down through the toilet and got all positions working for a couple of tank full's. It is now working on the full and 2/3 full positions.

I am now putting a cap of Tide in the black tank after it is dumped. If I travel I have a few gallons of water in the grey tank and put Tide in that also.
So far I have been able to keep the top two positions working.

Thudman · 12-08-2006, 06:35 AM

The pots on back of the circuit board (OnePlace) can be adjusted (plastic screwdriver) to increase resistance. Call Ventline 574-848-4491.

Do the Dawn thing first.

Thudman

Ptribbey · 12-08-2006, 07:52 AM

The direct contact sensors are very easy to replace. You remove what ever covers to get to the probes (each model differs). The probes themselves are nothing more than a rubber boot with a nut in the boot. The screw with wire attached just screws into the boot. A trick to remove the old boot is to use a razor blade and cut the flange of the rubber boot off and the remainder of the boot will fall into the tank and will wash out the next time you wash the tank. The set of (4) probes cost $5.00 at Winnebago. I had purchased the noncontact sensor system from Winnebago ($240.00) to upgrade my probes but since my contact type are so easy to maintain I haven't bothered to upgrade yet.

Bill Gotthelf · 12-08-2006, 03:45 PM

The 04's have external sensors. Fill tanks (both gray and black) 1/2 full with clean water, after dumping them and then add a 1/2 cup full of Tide Laundry or Dawn dishwashing soap.Drive to the next campground as this method will work great to clean inside of both tanks and help to get rid of odor. Dump the tanks when you get to the next campground.

NR4A · 12-11-2006, 02:54 PM

It worked like a Charm !!!!

I didn't have any Tide on-hand, but did have some liquid Sun laundry detergent. Flushed the tanks as usual, filled them with fresh water and added a cup of Sun (found at your dollar store cheap) - then dumped the tanks after a couple of hours.

The One Place shows empty when it is empty once again!!!

Thanks for all of the input on this forum - you'd think after 30 years of RVing I would have learned of this trick before.