Fuel Guage Sending Unit
- Thread starter Rick D
- Start date
I have been very satisfied with my Wema sensor for my fuel tank. I replaced a Moeller arm type with a Wema rod type sensor at the recommendation of others here on this site. It's been seven years with no issues.
Still have a Wema sensor in the fuel tank since 1998 when the boat was new and not a problem to date. Mind you, the same sensor in the holding tank usually crapped out 
in a week. Got rid of it the following year.
in a week. Got rid of it the following year.
what seems to be the problem with them?... moeller attempts to build good stuff and they stand behind their products.
but the sending units may be an outsourced device, and there may be an alternative or competitor model that will fit the application.
have you contacted them directly to discuss the issue?... they are friendly and helpful people to deal with.
I deal with fuel gauge and sending unit problems on a weekly basis and even though parts in general do fail and need to be replaced, I have never experienced a fuel gauge system that continually needs parts replaced. its a simple system with a gauge that reads the resistance to ground that the sender creates when the float is moved.... have you ohm'ed the unit to see if its completely dead or just has dead spots in it that lets the continuity drop away at times?...
but the sending units may be an outsourced device, and there may be an alternative or competitor model that will fit the application.
have you contacted them directly to discuss the issue?... they are friendly and helpful people to deal with.
I deal with fuel gauge and sending unit problems on a weekly basis and even though parts in general do fail and need to be replaced, I have never experienced a fuel gauge system that continually needs parts replaced. its a simple system with a gauge that reads the resistance to ground that the sender creates when the float is moved.... have you ohm'ed the unit to see if its completely dead or just has dead spots in it that lets the continuity drop away at times?...
sounds like a stray current problem. Current fromt he unit should only go through the returen ground but any path to ground that presents itself, like the fuel covering any part of the electrical path.Since the unit is supplied with voltage and has a dedicated return that can lead to the tank being a potential ground if there is any leakage. Is your tank grounded? and does the sending unit base have continuity with the tank
All I can offer is you are using DC here and you might be seeing galvonic corrosion due to the polarity of the sending unit. anodes (- side of things) loose material (like zincs) so I'm thinking reverse the polarity of the wires to make the unit + so it does not corrode or isolate the unit with plastic screw.
All I can offer is you are using DC here and you might be seeing galvonic corrosion due to the polarity of the sending unit. anodes (- side of things) loose material (like zincs) so I'm thinking reverse the polarity of the wires to make the unit + so it does not corrode or isolate the unit with plastic screw.
This will show you how to test and looks at the different types of fuel senders and their reliability..
Testing A Fuel Sending Unit (LINK)
Since we've owned Belle-Vie I've always trusted our fuel gauge, but then again I never let it go below a half a tank according to the gauge. Well this past season on our return trip I was quite some distance from a fuel station. I had decided not to top off at Echo Bay, our last stop, and the tank gauge was right at a half a tank.
Still about 70 miles from Roche Harbor to clear customs, I went below to check on the fuel status and to my surprise it read dead empty. Whoa! I knew my cruising buddy had ten gallons in two jerry cans so I put him on notice that I might need it. No problem.
Then I thought to double check using my versatile two foot long 3/8" dowel. I pulled the gauge and found that I still had 35 gallons of fuel to get me home. Whew! One of these days I will check to figure out why it drops to empty once the tank reaches half full. For now I will trust my dowel when the amount of fuel in the tank becomes a question.
Our tank gauge is some sort of manual device. The gauge itself gives a reading based on a simple magnetic rotation of a component located inside the tank. There is no physical or electrical connection between the analog gauge and the tank level sensor. Maybe someone here knows more about the device and can share their knowledge.
Still about 70 miles from Roche Harbor to clear customs, I went below to check on the fuel status and to my surprise it read dead empty. Whoa! I knew my cruising buddy had ten gallons in two jerry cans so I put him on notice that I might need it. No problem.
Then I thought to double check using my versatile two foot long 3/8" dowel. I pulled the gauge and found that I still had 35 gallons of fuel to get me home. Whew! One of these days I will check to figure out why it drops to empty once the tank reaches half full. For now I will trust my dowel when the amount of fuel in the tank becomes a question.
Our tank gauge is some sort of manual device. The gauge itself gives a reading based on a simple magnetic rotation of a component located inside the tank. There is no physical or electrical connection between the analog gauge and the tank level sensor. Maybe someone here knows more about the device and can share their knowledge.
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I replaced a Wema in my hold tank with a new Wema 2015. I also "flush/rinse" my hold tank 3 times, once a year. They work fine.Still have a Wema sensor in the fuel tank since 1998 when the boat was new and not a problem to date. Mind you, the same sensor in the holding tank usually crapped out
I did that with both diesel and water electrical/float type senders.
Both worked on the "bench" (just like your test) and on reinsertion didn't work.
My diesel had a plastic shaft and not the current Stainless Steel Wema.
@Maine Sail you might add that the "float" freely move up and down the shaft in the vertical position (my diesel plastic shaft sender had slightly warped and was "hanging") and should show a incremental change in value ( 0-100%)
Plus the water one was stainless shaft.
Finally I tested it in water, in a bucket. The float sank to the bottom.
The old float's coating was evidently not compatible with chlorinated water. The new ones are!
You might add to bench test and verify calibration the sensor in a bucket of water. I would suspect that Wema would use the same specific gravity float on ALL off their sensors. You can call and ask them.
Jim...
PS: I calibrate my Diesel sender each time I fill to make sure it is a working SAFETY device. Check my post#16 on how..
http://forums.sailboatowners.com/index.php?threads/diesel-used-per-hour.173796/#post-1231973