Black Water Tank

[Don Stewart]

Hi All, I am new to the forum and Beaver motorcoaches. We just purchased a used Contessa (2002/2003) triple slide Tuscany. We just took it out on our first shake down to find out what work needed to be done to bring it up to par. We found that the black water tank fill indication on the CMP panel continually shows at 85% full no matter what I do. It seems the sensor may be impaired in some manner. We don't know if this is a lever machanism or some type of sensing strip, or even how to access it. Any suggestions would be most appreciated.

[Tom and Pam Brown]

Don, first welcome!

I had similar issues with mine, first I used the black tank wash connection several times then I dumped my ice cooler remnants into the tank before my return trip.  That fixed mine, good luck.

[Gerald Farris]

Don,
Most likely your problem is just dirty sensor probes. You can usually just clean them with the black water tank flushing system.

Gerald

[Don Stewart]

Thank you Tom and Gerald, I used the santflush one time with no change. I like the idea of ice cubes and a semi-full tank, we will try that. Would anyone on the site know of a service manual that would show the location of the sensors on the tank and how to access them. We could also use a wiring diagram, the owners manual for the 2002 Contessa are not all that explanatory. We are in the process of going through all of the documentation that came with our motorhome.

[Steve Huber Co-Admin]

Don,
If you 02 is like my 01 Contessa, the tanks can be accessed by removing the panel behind the 3rd large bay door on the passenger side. The tank probes are not easily removed. I would try ice etc first. Also, try adding 48 oz of Pine-Sol and 1/2 cup of Calgon bath beads to an empty black water tank. The hook a hose to the black water flush system and let it run until the tank is full. (Suds will come out of the toilet). Let sit for an hour or so and drain the tank. Worked for me.
If you are going to be at the Kerrville rally, consider contacting these folks. They will clean your tanks right at your site. They did a good job on my Marquis this spring.
http://rvholdingtankservices.com/
Steve

[Gerald Farris]

Don,
There are two types of tank sensors, and I am not sure which one the 2002 Contessa used. If your coach has a pressure sensor, it is located near the bottom of the tank on the left end (driver's side) of the tank. This type sensor can be recalibrated if the sensor is not defective, but if it is defective, it must be replaced. Cleaning the tank rarely corrects errors on this type sensor.

The other type sensor uses brass pins through the right end (passenger's side) of the tank. With this type sensor it measures the conductivity between the pins at different depths to determine the amount of material in the tank. The sensors on this type unit are not replaceable and the only correction for sensor error is cleaning the inside of the tank.

If your tank sensors change readings every 5%, you have pressure sensors, but if the readings change in larger amounts like from 30% to 50%, you have the brass pin type sensors.

Gerald

[Gerald Farris]

Don,
There are two types of tank sensors, and I am not sure which one the 2002 Contessa used. If your coach has a pressure sensor, it is located near the bottom of the tank on the left end (driver's side) of the tank. This type sensor can be recalibrated if the sensor is not defective, but if it is defective, it must be replaced. Cleaning the tank rarely corrects errors on this type sensor.

The other type sensor uses brass pins through the right end (passenger's side) of the tank. With this type sensor it measures the conductivity between the pins at different depths to determine the amount of material in the tank. The sensors on this type unit are not replaceable and the only correction for sensor error is cleaning the inside of the tank.

If your tank sensors change readings every 5%, you have pressure sensors, but if the readings change in larger amounts like from 30% to 50%, you have the brass pin type sensors.

Gerald

[Matthew Harger]

Mine were doing the same thing, showing full, no matter how I cleaned the tanks.  I'm sure it was probably from years of neglect and improper upkeep from the previous coach owner.  Anyways, I took a chance and bought into this guys product and installed them.  Took about an hour to do both gray and black tanks and have had nothing but success and good accurate readings since.  Our coach had the pin sensors and I  just mounted the new ones next to the old and moved the wires over.  

I'm sure there other options but these were the ones I got.

 http://www.rvprobes.com/howitworks.html

[Dick Simonis]

For what's it worth, I've had great success dropping a couple of the dish washing detergent "pillows" down the toilet before leaving a park.  If there are a few gallons of liquid in the tank and the road is sufficiently winding, I also arrive at the next stop with a functioning read out.  Straight and level doesn't do much good but turning and bouncing seems to do the trick.

[Greg Kamper]

I had the same problem with my 2000 Pat Thunder. But the only tank sensor that worked was the grey. Fresh always read empty and the black was always full.  I ended up installing the Seelevel from Garnet. I love it. The hardest part was routing the wires inside the coach and deciding where to mount the readout gauge. I ended up putting it in the bathroom cabinet above the toilet. That way I didn't have to tear everything apart. I could have put it on the hallway wall, but I was too scared to drill through the beautiful woodwork.