Waste water gauge

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Sessa Lel

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Hi
I probably know the answer to this question, but just want to make sure.
My Osculati waste water gauge goes straight to full when turning on toilet switch, I have disconnect the wires at sender unit, sill the same, disconnected all wires behind gauge apart from 12v and earth, gauge goes straight to full, I'm sure it's a faulty gauge, does anyone agree with me?
 
Sessa Lel said:
Hi
I probably know the answer to this question, but just want to make sure.
My Osculati waste water gauge goes straight to full when turning on toilet switch, I have disconnect the wires at sender unit, sill the same, disconnected all wires behind gauge apart from 12v and earth, gauge goes straight to full, I'm sure it's a faulty gauge, does anyone agree with me?
Click to expand...
Might be asking a stupid question here - but is the tank empty?
 
ylop said:
Might be asking a stupid question here - but is the tank empty?
Click to expand...
Hi, it may well be empty, but as stated, I have disconnect the sensor wires on the back of the gauge, only have 12v wire connected as soon as I attach the earth wire the gauge shoots to full.
Wouldn't make any difference but tried connecting earth before 12v, still the same. How would tank being empty have any bearing on gauge shooting up too full?
 
Sessa Lel said:
Hi, it may well be empty, but as stated, I have disconnect the sensor wires on the back of the gauge, only have 12v wire connected as soon as I attach the earth wire the gauge shoots to full.
Wouldn't make any difference but tried connecting earth before 12v, still the same. How would tank being empty have any bearing on gauge shooting up too full?
Click to expand...
Depending if the sensor is European or US standard then disconnecting the sensor may result in it showing full (assuming this is a classic resistance sensor). I can never remember which is which but I think European gauges show full when open circuit/disconnected, and empty when very low resistance. Now if I followed you are getting full when you turn on the toilet switch (I'm not sure what that switch powers, but if it is the gauge) then the first presumption would be the tank is full. Tanks do get blocked so if I had those symptoms I'd be checking the actual tank level before replacing sensors or gauges. You could also pop a multimeter on resistance setting across the sensor connections at the tank.
 
ylop said:
Depending if the sensor is European or US standard then disconnecting the sensor may result in it showing full (assuming this is a classic resistance sensor). I can never remember which is which but I think European gauges show full when open circuit/disconnected, and empty when very low resistance. Now if I followed you are getting full when you turn on the toilet switch (I'm not sure what that switch powers, but if it is the gauge) then the first presumption would be the tank is full. Tanks do get blocked so if I had those symptoms I'd be checking the actual tank level before replacing sensors or gauges. You could also pop a multimeter on resistance setting across the sensor connections at the tank.
Click to expand...
Hi
I had a reading of 15 Ohms, at the sender, so I assumed I had european sender, 0 Ohms empty and 190 Ohms full. Still can't work out if the sender is not connected would the gauge shoot to full?
Thanks
 
Sessa Lel said:
Hi
I probably know the answer to this question, but just want to make sure.
My Osculati waste water gauge goes straight to full when turning on toilet switch, I have disconnect the wires at sender unit, sill the same, disconnected all wires behind gauge apart from 12v and earth, gauge goes straight to full, I'm sure it's a faulty gauge, does anyone agree with me?
Click to expand...
More likely a faulty sender, easy to diagnose.
 
Sessa Lel said:
Hi, I'm confused, if the wires from the sensor are not connected at the back of the gauge (isolated ) how can it be the sensor?
Click to expand...
Mmmm, I may have misread the your original post, if the sender is completely out of circuit then maybe the gauge, do you have the wiring diagram for the gauge?
Doe the gauge have 3 connections, Pos, Neg and G or S?
 
BB1 said:
Mmmm, I may have misread the your original post, if the sender is completely out of circuit then maybe the gauge, do you have the wiring diagram for the gauge?
Doe the gauge have 3 connections, Pos, Neg and G or S?
Click to expand...
20250814_143050.jpg
12v, earth, light, and sender signal.
 
if you have a reasonable reading from the sender alone in Ohms as you do, sender should be fine.
I'd try wiring the gauge to power only and add a reasonable resistor (or a potentiometer if you happen to have one around) to see if it respods as it should.
Pretty sure that one side of resistor goes to GND other to S. If needle behaves, then I'd search the wiring.

TBH, I'd first get both sender and gauge on a table (I know not the nicest things to have there!) and wire them with short pieces of known good wires and spades and see what happens.
I'd give a 80% to wiring issues, 20% gauge and since wiring is cheap, I'd start from that
:)

cheers
V
 
vas said:
if you have a reasonable reading from the sender alone in Ohms as you do, sender should be fine.
I'd try wiring the gauge to power only and add a reasonable resistor (or a potentiometer if you happen to have one around) to see if it respods as it should.
Pretty sure that one side of resistor goes to GND other to S. If needle behaves, then I'd search the wiring.

TBH, I'd first get both sender and gauge on a table (I know not the nicest things to have there!) and wire them with short pieces of known good wires and spades and see what happens.
I'd give a 80% to wiring issues, 20% gauge and since wiring is cheap, I'd start from that
:)

cheers
V
Click to expand...
Thanks, I have managed to pickup a gauge for £21, (so not the end of the world) and could probably send it back, so for me the easiest is gauge first, and if not then I will look at wiring (very long run from engine compartment to gauge panel.
 
good, in some cases I had to to take the easiest to remove off and next to the other one and check that everything worked. most cases was a wiring fault...
 
vas said:
good, in some cases I had to to take the easiest to remove off and next to the other one and check that everything worked. most cases was a wiring fault...
Click to expand...
Hi
Went down to the boat, disconnected the sender unit, Connected Ohm meter, open circuit! Connected wires to gauge at sender unit together, gauge went straight to empty, so looks like the sensor that was fitted 8 months ago has failed!
Now I know.
 
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wasn't expecting that tbh!
a simple device like that failing in short period, I'd question the toilet switch and what it does can you explain?
Is it factory fitted to simply turn on and off the gauge so that it doesn't run all the time, or it does other things as well?
 
vas said:
wasn't expecting that tbh!
a simple device like that failing in short period, I'd question the toilet switch and what it does can you explain?
Is it factory fitted to simply turn on and off the gauge so that it doesn't run all the time, or it does other things as well?
Click to expand...
There are 2 switches on control panel 1:WC, which turns on the toilet pump and the gauge ( once this is on, there is a switch in th head for flushing toilet )
Once on, the gauge reads level in tank (or in my case it stays on full)
2: rocker switch for WC pump, which powers the masarater pump next to holing tank to empty tank at sea.
 
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