Holding tank gauge sender inaccurate readings

[Jhawk123]

I have a 2017 Bavaria R40 Fly and I am getting inaccuate reading from the holding tank sensor(gauge). When tank is full, the tank status says its only 50% or there abouts. I have cleaned the sensor, and I have replaced the sensor, but both give the same readings. Any ideas?

 

[Norman_E]

You need to explain the sender type. The sort that work by means of a float on an arm, or the vertical tube type with a sliding float. Either can get stuck and the lever arm type need to be positioned so that the arm cannot hit the side of the tank. The other potential problem is that both gauge and sender need to be compatible, i.e. working over the same resistance range.
The lever arm type of sender can be adjusted to some extent by bending the arm, so if the float on yours has reached the top of the tank, check whether bending the arm down a bit lets you get a higher reading on the gauge.

 

[Jhawk123]

Thanks for your reply Norman
I have a UTV35 Ultrasonic Sensor. There is no arm, tubes, or sliding float. There are no moving parts. It operates by ultrasonic signals.

 

[coopec]

Thanks for your reply Norman
I have a UTV35 Ultrasonic Sensor. There is no arm, tubes, or sliding float. There are no moving parts. It operates by ultrasonic signals.

I have no idea what you are talking about. But if you want to know about dip-sticks......

Bavaria UTV35 Ultrasonic Sensor buy now | SVB

Is this relevant?

 

[davidaprice]

I know nothing about this kind of sensor (I myself have Gobius ultrasonic sensors, which work differently). This instruction manual suggests that in holding tanks you might need a 'focus tube': https://www.philippi-online.de/fileadmin/philippi/Public/Content/articles_manual/UTVgb.pdf . Also notice that the sensor will produce incorrect readings when the liquid surface is <5cm from the sensor (mounted in the top of the tank facing down) - might this be the case when the tank is full?

 

[vas]

I also have a Philippi Ultrasonic sensor for the black tank. The idea of having to clean the other types wasn't appealing
two Qs to OP:
1.has the gauge ever work correctly? what does it show when tank is empty, more or less? Give us the range
2.can you remove the gauge and use v.short cables to wire it to the sender, do you get the right values?

If the answer to 1 is no, I'd question the match between sender and gauge!
if 2 is the solution the cable is wrong (but I doubt it!)

V.

 

[Norman_E]

According to the SVB website that ultrasonic sensor outputs a voltage from 0.5 volts at empty to 5 volts at full, working the gauge by voltage rather than by resistance like the other types. First step to diagnose the problem should therefore be to connect a voltmeter to the output wires and measure the actual voltages you are getting through the range from empty to full. If the sender does output 5 volts at full, disconnect the gauge and check the voltage at that end of the output wires in case the wiring is the problem. Another test would be to check the gauge itself. Disconnect its input wires and use three torch batteries in series to provide 4.5 volts and see if it reads close to full. It is possible that your gauge needs a higher voltage range, is it marked?

 

[Norman_E]

One quick check to carry out. The sender has three wires which are presumably 12 volt + 12 volt - and Output. That supposes that the gauge itself provides the negative connection for the output circuit. Make sure that the gauge is properly earthed and preferably connected back to the same negative or earth connection as the sender. if the gauge has high resistance to earth you will get low readings.

 

[cpedw]

According to the SVB website that ultrasonic sensor outputs a voltage from 0.5 volts at empty to 5 volts at full, working the gauge by voltage rather than by resistance like the other types.

My reading says 2.5V full so don't use 2 x1.5V batteries.