BAC Forum
General Boards => Technical Support => Topic started by: Dennis Belfils on July 18, 2019, 07:29:04 PM
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Hello, I have replaced all three tank sensors. Both Gray & Black went well, but I cannot get the Fresh to calibrate. Tried it both full & empty. The readings that appear on the screen say the same raw value @ 1023 for full or empty. I have tried the tank height method in millimeters -19, but still get erroneous readings. I also tried a new communication cable from the sensor to the module. Any ideas?
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I am curious about this myself. My gray and black water tanks read correctly, but my freshwater tank always reads full at 102 gallons.
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You can try a bit of experimenting with swapping the sensor cables into the small Alladin box where the three sensor cables come together (mine is in the latched bay in front of the passenger side rear tire). If you swap the communication cables between the gray and fresh water connections, you can determine if the problem is with the sensor (or its cable) or within the Alladin system. If the failure to communicate follows the cable when you switch from the fresh to the gray, then the problem is in the cable or the sensor. It is common for the RJ11 (telephone jack) connectors to corrode and fail to connect. Cleaning all the connections with contact cleaner and compressed air often solves the problem. Good luck with your troubleshooting.
Richard
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Thanx Richard. I did give that a try, problem did not move. Am now going to try playing with the Fresh empty raw figures as it should not be 1023, IMHO. I am now suspecting a bad module. but can't justify spending $300+ for a used one. I am wondering how the Raw numbers are figured. Is it programmed into the module? Or does it come from the sensor & the module no longer sees it. Raw numbers for the Gray & Black empty are no where near the 1023 that the Fresh says......
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I think the raw #'s are 'bit counts', a digital value based on total loop resistance (sensor, cable, and tank module). Another guess, the sensor's resistance value changes as the tank level changs and the tank module converts this resistance to a digital value so it can be passed over the comm cable to the Aladdin display. Not sure what my empty raw value is, but I don't think there is any issue with playing around with the value.
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Thanx Bill. That's what I thought it might be. Have tried playing with values, but no success. With the full & empty raw values being the same @ 1023, the T.I.M. must be screwed up. Will have to live with it for now...……..
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I have always preferred mechanical devices rather than electronic for water sensors. In my case ('06 Monterey), the physical water tank is translucent, so I just took a magic marker and marked the outside of the tank in 10 gallon increments on the side of the tank. That way, a quick opening of the bay door and I can see exactly how much water I have left. On my previous coach, the tank was ABS black plastic, so I could not see through it. I added a small fitting on the bottom of the tank with a clear plastic tube attached up the side of the tank with gallon markings on the clear plastic tube. Since water seeks its own level, I could always tell how much water I had left by looking at the clear plastic tube. Where there is a will, there is a way.
Richard
p.s. On the ABS plastic gray and black tanks, I would often use a lazar temperature gun on the outside of the tank. The tank would be cooler where there was liquid on the inside.