Another Fuel Gauge repair

[Gunni]

Need some advice from you folks skilled in the dark arts (electricity). VDO fuel gauge and float sensor on a Beneteau. It was working accurately until late last year. The sender float checks out within the specified Ohm range (in fact my Ohm gauge has become my temporary fuel gauge). The cockpit VDO gauge checks out to VDO spec. So I am down to wire. I cleaned all the contacts, no go. It looks like a 20 foot run, two 18ga. conductors. Interestingly, the negative comes the whole way to the gauge to ground. Re-running new wire is next (major snaking job). One last Hail Mary is to send sender ground to a nearby DC ground and hope that solves the problem.

Any thoughts appreciated.

 

[centerline]

Need some advice from you folks skilled in the dark arts (electricity). VDO fuel gauge and float sensor on a Beneteau. It was working accurately until late last year. The sender float checks out within the specified Ohm range (in fact my Ohm gauge has become my temporary fuel gauge). The cockpit VDO gauge checks out to VDO spec. So I am down to wire. I cleaned all the contacts, no go. It looks like a 20 foot run, two 18ga. conductors. Interestingly, the negative comes the whole way to the gauge to ground. Re-running new wire is next (major snaking job). One last Hail Mary is to send sender ground to a nearby DC ground and hope that solves the problem.

Any thoughts appreciated.

you didnt mention if you tested each of the existing wires for continuity, which is easier to do than testing the components themselves... and much, much easier than running new wires in their place

disconnect one end of the sender wire and use a continuity tester to test the sender wire from the gauge to the tank.
and do the same for the ground wire from the tank, to where it returns to ground near the gauge... (the ground wire MUST connect to the sender body and NOT to the bonding lug on the tank itself) THEN test the point where the ground connection is near the gauge to the ground circuit of the boat... you will most likely find the problem in the ground circuit somewhere.

if you have power to a properly working gauge, and you have a properly working sender, then it is only the wire that is left to test.

 

[rpwillia]

Troubleshooting

I had a problem with my fuel gauge and voltage meter last year. I checked everything out and finally decided the gauges were off so I replaced them and all has been fine. Here are some notes that I wrote down from that.

The fuel gauges are Teleflex; in the West Marine Catalog is a "Teleflex" 'Universal electric fuel gage and sending unit", sending unit Model #547406 TELEF#90424P which costs $29.99. To order a new gauge, contact Lonnie at Seaward (562-699-7997 x213),

Lonnie believes there are far too many change-outs that are simply the result of faulty wiring. There are only three parts for the fuel gauge system.

1. The gauge itself (less likely to fail)
2. The wiring between the gauge and fuel tank (more likely to fail)
3. The tank sender/float assembly (more likely to fail)

To access the fuel tank sending unit you need to remove it from the top of the tank where there is a round plate with 5 screws. Sender is attached to the bottom side of this plate. You need a stubby Phillips screwdriver as there is not much clearance above the tank. The gauge is a volt/ohm meter and the sender/float assembly is a variable resistor on a pivot style float. If it is reading full continuously the gauge is bad or, most probably, there is a short in the wire from tank to gauge.

• When tank is empty, float arm hangs almost straight down
• When tank is full, float arm is floating horizontally and touches the top of the tank
• The arm must have nearly a full 90 degree unobstructed swing
• You can loosen the set screw(s) on the sender and rotate the sender 90°
• Ensure sending unit is oriented correctly as the float rotates and may hit the side of the tank and not read correctly

 

[Gunni]

Thanks, I am seeing variable resistance values when I connect the sender wire to the gauge. I am going to run a temp sender and ground direct from the tank to the gauge and see if that works.

 

[Dan Johnson]

Hey Gunni...

Here's a pair of PDF's on Teleflex's gauges--suspect VDO's to be similar

 

[Lee Hadjiosif]

Need some advice from you folks skilled in the dark arts (electricity). VDO fuel gauge and float sensor on a Beneteau. It was working accurately until late last year. The sender float checks out within the specified Ohm range (in fact my Ohm gauge has become my temporary fuel gauge). The cockpit VDO gauge checks out to VDO spec. So I am down to wire. I cleaned all the contacts, no go. It looks like a 20 foot run, two 18ga. conductors. Interestingly, the negative comes the whole way to the gauge to ground. Re-running new wire is next (major snaking job). One last Hail Mary is to send sender ground to a nearby DC ground and hope that solves the problem.

Any thoughts appreciated.

Gunni,
The easiest way to check for continuity of hidden wires is as follows:
1. Disconnect the wires from both ends, gauge and sender and make sure the ends don't touch anything or are taped.
2. From the sender side (or the gauge side if easier) using an ohmmeter, check for continuity for each wire with the ground(tank). If it's pinched, you will get closed circuit(buzz).
3. If both wires check out OK, then twist the two wires together (+ & -) on one side and go to the other side and check for continuity of the red and black wires with the ohmmeter again. If you get a buzz, the wiring is NOT the problem. I learned this from a professional telephone company electrician.
4. Make sure that the wires a truly removed from any power source before you twist the red and black together!! Good Luck
Lee

 

[FourPoints]

if you're going to change the sending unit, don't buy those crappy ones with the long arm and float, get a Wema. http://www.wemausa.com

Much more reliable.

 

[Gunni]

Gunni,
The easiest way to check for continuity of hidden wires is as follows:
1. Disconnect the wires from both ends, gauge and sender and make sure the ends don't touch anything or are taped.
2. From the sender side (or the gauge side if easier) using an ohmmeter, check for continuity for each wire with the ground(tank). If it's pinched, you will get closed circuit(buzz).
3. If both wires check out OK, then twist the two wires together (+ & -) on one side and go to the other side and check for continuity of the red and black wires with the ohmmeter again. If you get a buzz, the wiring is NOT the problem. I learned this from a professional telephone company electrician.
4. Make sure that the wires a truly removed from any power source before you twist the red and black together!! Good Luck
Lee

Good stuff Lee! Can you explain your comment #2 above - I don't understand what you are describing. Thanks.

 

[Lee Hadjiosif]

Good stuff Lee! Can you explain your comment #2 above - I don't understand what you are describing. Thanks.

If a wire is pinched and grounded where you can't see it, it will be at the same potential as the ground.(battery - or the tank which I'm sure is grounded). If the ohmmeter shows open circuit between the end of the wire and the ground, then you are OK. If you show closed circuit, then the wire is touching ground somewhere. I hope this helps.
Lee

 

[Gunni]

Roger that Lee! Thanks - G