Water gauge problem

[Bow42]

My water tank gauge seen to stay on almost empty .
When disconnected the wires at the tank , the gauge goes to full , so the gauge is working .
Testing the Volts at where it goes into the sender unit , its showing 9.6 v .
Shouldn't that be 12v plus ?

Don't want to take the gauge out at this point has somebody at sometime had it sealed .

 

[benchmark]

From the WEMA website:
How to test if a sender is Working properly.

Disconnect the sender wires at the sending unit.
Connect the 2 wires to an ohmmeter or multimeter and set signal to resistance.
Take measurement of the sender at empty and full positions.
This can be done by either draining and then re-filling the tank which the sending unit is installed, or remove the sending unit from the tank and then manual operate the float by hand.
For American Standard, the meter will show 240 ohms at empty and 30 ohms at full.
For European Standard, the meter will show 0 ohms at empty and 180 ohms at full.

How to test if the level gauge is operating correctly?

Make sure power to the gauge is not on.
Disconnect the black wire on the gauge to the sender. Leave enough wire at the gauge end to work with.
Turn on the power to the gauge
Inspect the
American standard gauges (240-30 ohms) will show Empty. Ground the black wire, and the needle will go to Full
European standard gauges (0-180 ohms) will show Full. Ground the black wire, and the needle will go to Empty

 

[johnalison]

I went through this last year, but I had 12+ volts at the unit. I tested it according to the above instructions and the old unit was clearly knackered.

Can you not access the unit from an inspection hatch and move the slider to test the resistance? If the unit is then shown to be working, then the loss of volts will be shown to be the cause, but it sounds as if this needs looking to anyway.

 

[Bow42]

I went through this last year, but I had 12+ volts at the unit. I tested it according to the above instructions and the old unit was clearly knackered.

Can you not access the unit from an inspection hatch and move the slider to test the resistance? If the unit is then shown to be working, then the loss of volts will be shown to be the cause, but it sounds as if this needs looking to anyway.

There no way of getting into the tank so unless I take it out there no way of moving the sender .
I don't think the lost of Volts as anything to do with any faults, as I am testing the red and black that going to the sender just as it enter the sender from where ever ,
I don't want to put a 12v to it test until I know for sure there should be 12v there in the first place .

 

[PaulRainbow]

My water tank gauge seen to stay on almost empty .
When disconnected the wires at the tank , the gauge goes to full , so the gauge is working .
Testing the Volts at where it goes into the sender unit , its showing 9.6 v .
Shouldn't that be 12v plus ?

Don't want to take the gauge out at this point has somebody at sometime had it sealed .

You don't say what make/model of gauge, but i wouldn't expect the sender unit to have +12v at the sender. Frinstance, the Wema unit being discussed has a pink wire connected to 12v neg and a black wire connected to the instrument.

 

[johnalison]

You don't say what make/model of gauge, but i wouldn't expect the sender unit to have +12v at the sender. Frinstance, the Wema unit being discussed has a pink wire connected to 12v neg and a black wire connected to the instrument.

Since the meter at the panel is basically a voltmeter, the volts being measured do matter. For example, my water and fuel meters read slightly differently when the mains charger is connected and the voltage goes to over 14v. I'm fairly sure that the volts at my sender unit were over 12.

 

[PaulRainbow]

Since the meter at the panel is basically a voltmeter, the volts being measured do matter. For example, my water and fuel meters read slightly differently when the mains charger is connected and the voltage goes to over 14v. I'm fairly sure that the volts at my sender unit were over 12.

Most, if not all, of the fuel/water gauges that i have come across have a 12v positive at the gauge, 12v negative at the sender and a wire from the sender to the gauge. Of course, i doubt if i've seen every gauge that was ever made, so we really need to know what the OP has.

 

[sunquest]

There no way of getting into the tank so unless I take it out there no way of moving the sender .
.

You could try disconnecting the wire from the sender terminal on the guage and measuring the resistance between the sender wire and sender terminal. Incidentally my fuel gauge is reading incorrectly and during testing found a resistance of 110 ohms between the earth wire and earth connection on the gauge. Investigations ongoing.

 

[rogerthebodger]

You need to find out what type water gauge you have.

There are 2 types

1) resistance type
2) 4 to 20mA current measuring type.

The resistance type can have 2 or 3 wires connected to the sender where the current type will only have 2 wires and can have the 12vDC at the gauge or at the sender.

VDO do both types so the mane of the manufactures is most important.

My own setup for both water and fuel are the 4 to 20mA type using tubular capacitive types and a VDO 4 20mA gauge