Another Fuel Gauge Issue

Ralph Johnstone · Dec 18, 2011

If It Goes Backwards ......................................

................... just maybe it's an electrical problem.

If you are sure you haven't changed any wiring prior to the problem rearing its ugly head, try checking if there is any voltage difference between your battery neg. terminal and the ground right at your meter. OR just run a wire from your meter ground terminal right to your battery neg. with a piece of scrap wire.

Please let us know what happens.

Rich Stidger · Dec 18, 2011

Rocknoids,

I think the problem is that the sender wire from the sender to the gauge input is open. Attached is a document that describes your failure mode and tells you how to T/S the gauge and sender.

To the best of my knowledge, all of these gauges work the same way regardless of the manufacturer. These documents were written by Teleflex.

CYA disclaimer: YMMV

Maine Sail · Dec 19, 2011

I always start with the sender because the test is easy & quick. Set your Ohm meter to resistance/ Ω and connect red to the center stud and black the flange of the sender. This generally works better with an analog volt meter but digital ones work too. You should see readings that are close to 240 Ω when empty, about 100 Ω at half and 33 Ω at full.

If you see these numbers the sender is working correctly. If you have the sender out move the float up and down manually and watch your Ohm meter for any drop outs.

You can then test the continuity of the feed wires. It is often a failed sender but can also be a bad or corroded connection. The wires to the sender from the gauge are not carrying voltage, they read resistance, so you will not measure "12V" at the sender end. The gauges also can go bad but I find the senders go bad more often.

Bill Roosa · Dec 19, 2011

You have the ground wire from the sender to the gauge picking up 12 volts somewhere. The gauge is just an ohm meter (sender is just a variable resistor attached to a float) with a “funny face” that reads the tank level instead of ohms and when you try to get it to measure voltage it goes "full scale" In this case full scale negative so the ground is getting voltage.
Check the wires behind the panel by turning the motor on and wiggling them to see if the gauge starts reading correctly. if that does not yield something trace the wire to the sender looking for a bear spot. I'm thinking it has to be near the panel as the rest of the wire run probably does not have any power wires near it to supply the 12 volts.

Chuckbear · Dec 19, 2011

My fuel gauge has a bit of a different issue. It seems to read fine and read correctly, EXCEPT, it reads backwards so when at full it shows empty and at empty shows full and everything in between is reversed. Any suggestions? It has worked this way for as long as we have owned the boat. The PO must have lived with it. I have checked and rechecked all of the wiring and it appears to be correct. Chuck

Maine Sail · Dec 19, 2011

Chuckbear said:
My fuel gauge has a bit of a different issue. It seems to read fine and read correctly, EXCEPT, it reads backwards so when at full it shows empty and at empty shows full and everything in between is reversed. Any suggestions? It has worked this way for as long as we have owned the boat. The PO must have lived with it. I have checked and rechecked all of the wiring and it appears to be correct. Chuck

Chuck,

Is it a VDO gauge by any chance? I had that same issue with a VDO. After all the trouble shooting steps I replaced it with a Teleflex gauge and problem solved. The VDO should have been the same as the Teleflex but was not for some reason and read backwards... Never seen this any other time except with one VDO gauge..???

Stu Jackson · Dec 19, 2011

Chuck, you could do as Maine Sail suggests.

Or:

1. leave it just as it is - every boat needs an oddity (other than like mine, which is the skipper!)

2. disconnect it completely and tell the next owner to use engine hours to measure fuel consumption (our fuel gauge hasn't worked since 1999 and i haven't run out of fuel yet)

Always somethin', isn't it?

Bill Roosa · Dec 19, 2011

VDO wants you to by their senders too. They wire it backward so full is high resistance and empty is low resistance. The rest of the free world has full as low and empty as high.
You could take the unit out and move the resistor ground to the gauge terminal and the gauge terminal to the ground. Or if it has two wires just reverse them. I don't think the latter is going to do anything but with VDO you never know. Also check for a third terminal on the sender. If it has three then you are in luck. One set will read high-low, another will read low-high and the remaining will either not show any change or read twice the resistance value. worth a look.

Chuckbear · Dec 19, 2011

The gauge says Kybor/Medallion on the face. I made a label with a label maker with an E and an F and stuck them on the gauge to show it correctly. Not at the top of my priorities right now so as long as I can see how much fuel I have in the tank, oh well. Chuck

Steve Dion · Dec 19, 2011

New ones are not that expensive ($40 for a Wema). You should get your electrical checked out before you decide to replace the sender.

http://www.wemausa.com/

check out the 25% discount at check out if you need to replace the unit.

woodster · Dec 19, 2011

Steve Dion said:
New ones are not that expensive ($40 for a Wema). You should get your electrical checked out before you decide to replace the sender.

http://www.wemausa.com/

check out the 25% discount at check out if you need to replace the unit.

you can get them from Bestfab in FL...go to there web site and then go to there ebay store on there site...i got mine from them for my water tank and my fuel tank ...both for $25.00 each and the have fuel pick up tubes as well for around 6 to 7 dollars ..and there shipping and responce time is great

regards

woody

Maine Sail · Dec 20, 2011

woodster said:
you can get them from Bestfab in FL...go to there web site and then go to there ebay store on there site...i got mine from them for my water tank and my fuel tank ...both for $25.00 each and the have fuel pick up tubes as well for around 6 to 7 dollars ..and there shipping and responce time is great

regards

woody

I believe your gracious host also sells WEMA sending units. Personally I prefer the mechanical senders with the magnetic capsule that reads the tank level. They seemingly last forever...

woodster · Dec 20, 2011

Maine Sail said:
I believe your gracious host also sells WEMA sending units. Personally I prefer the mechanical senders with the magnetic capsule that reads the tank level. They seemingly last forever...

thanks for the info...when i pulled them up i got a bad url address on the pages.....had no idea that they sold these.....oh well next time i will be able to recomend them as well....

regards

woody

Another Fuel Gauge Issue

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