Trouble shooting faulty water gauge

[SvenglishTommy]

Hi all,

My water tank guage isn't working and I have absolutely no idea where to start in terms of identifying the problem. The gauge is a wema gauge with a needle that is permanently in the full position. It has power as the light works, and I have had a look at the sensor which is the type that has a float on a stick in the water. The float moves freely up and down.

Anyone got any ideas on what to check for to find the problem, e.g. should I get a change in voltage from the sensor to the gauge or do they work in some other way?

Thanks,

Tom

 

[colind3782]

Fit a sight glass. Low-tech and cheap.

Colin

 

[dt4134]

It has power as the light works, and I have had a look at the sensor which is the type that has a float on a stick in the water. The float moves freely up and down.

It should be quite a simple circuit. Have you been able to unscrew the sensor and move it by hand to check what it does to the meter reading? Does it stay full whatever you do?

Assuming the sensor isn't stuck, then it is more likely to be an electrical problem. The symptom you describe of it showing full would make me look for short circuits somewhere.

Check the connectors at the meter just in case. You could also check the wiring hasn't been trapped somewhere and shorted. I'd guess it is more likely to be at the sensor. If it is the part of the sensor inside the tank and is nothing obvious you might have to look at a new sensor.

 

[VicS]

Not necessarily a short circuit.

Also check all the connections between gauge and sensor.

 

[David2452]

Check the resistance across the two cables at the sender (disconnected) they sould read 180 Ohms full and about 10 empty, if not then replace the sender. check the two cables to the gauge for voltage, If OK, reconnect and remove the same two cables at the instrument end and check resistance at that end, it should be about the same if OK suspect the gauge, if not then trace the cabling fault. It is possible that the readings may show 240 ohms empty and around 40 full, if so don't worry, it's just that you have a U.S. spec gauge and sender instead of the expected European one.

 

[tillergirl]

Have to say I had a float sensor and it was always getting stuck usually on full. It was simply that the float pivot was too stiff and needed lubrication which of course in water it didn't get. I got a different type of sensor and have had no probems.

 

[SvenglishTommy]

thanks guys, there is no conduction at all across the sensor wires, so I guess that is the problem. If I join the two wires to the meter then it goes to empty, so I guess the gauge is working fine. No way of fixing these sensors then?

 

[SvenglishTommy]

David, your comment about the resistance has now got me thinking about my fuel gauge. It works, but I get the feeling it is very wrong. When full it's full, but then seems to go down much faster than reality. Would this suggest a european sender with a US gauge? The gauges are wema, which is a US company I think, and both tanks have been replaced in Spain.

 

[rudolph_hart]

I fitted a Wema water guage on my boat a few years ago, and when I had a problem with it, these people were very helpful: www.wema.co.uk