NEED AN EXPERT ON FUEL GAUGE

[cdwood]

Re-did complete instrument panel with Faria Chesapeake SS Gauges. Cannot get fuel gauge to work. Have new gas tank with new sender. Everything checks out as per Ted @ Faria tech support.

Ohms out at less than 90 showing tank almost full.

Short the gauge and it pegs to full.

All wiring is new.

Faria replaced the gauge twice(3 different gauges) no change, always reads empty.

Have Navman fuel monitoring so not really dependent on gauge, just really frustrated that all but this gauge work beautifully.

Anybody know of something that may have been overlooked?

 

[seasick]

The sender may not be grounded.

If you disconnect the wire to the gauge at the sender, the gauge will read empty ( USA models), ground that wire and the gauge should read full. Note I said to ground the wire from the sender to the gauge at the sender

The sender should read about 40 ohms at full and 230 at empty.
So if all that checks out, the sender isn't grounded or the tank, if metal, isnt grounded.

 

[cdwood]

seasick, you got me thinkin'. If the tank was grounded to the main batt. and the gauges are running off the house batt. without a common ground between the 2 batts. could that be the problem?

I know the tank is grounded to main batt. but sender leads run up to instrument panel which runs off house batt.

Would a line between both batt. grounds resolve this?

 

[BobP]

All of your batteries should have a common ground bus.

 

[seasick]

All of your batteries should have a common ground bus.

Absolutely true. There should be a common between the batteries and it should be a decent gauge wire size.

 

[BobP]

Same size as positive cable used for battery switches will do. I use the Blue Seas Bus, 4x 5/16inch dia. terminals, as I recall.

He can connect a small gauge jumper with clip leads as a test, any gauge will do for the test.

 

[Boats Rock]

Run a jumper from the tank sender to the battery. Just to verify the ground.

 

[cdwood]

Will be verifying not only tank/sender ground but common ground between batteries.

THANKS GUYS, would love to put this issue to rest.

 

[BobP]

When you measured resistance of sender, did you disconnect all sender wires including ground wire to tank?

 

[cdwood]

Negative on that bob. Measured it at the gauge.

 

[BobP]

And you replaced the wiring between gauge and sender?

If the ground jumper between batts doesn't work, and you are out of tricks to try -

the multimeter you use only applies a small voltage and tiny current to excite the circuit to measure resistance.
The insulation if the circuit if compromised can work fine but not so at the operating voltage. Wiring can be tested by a megger to verify integrity.

No need to have a megger tester, just make up a two wire jumper and lay it on the deck up to the instrument and to the sender, disconnect all wires to sender, make sure neg ground wire to tank is intact and connected to your test wiring. Then see if that works. This test will isolate wiring as an issue.

Since you confirmed the gauge is good, the only thing left then is the sender unless you have two tanks - then the selector switch has to be verified.

 

[cdwood]

Single tank, all new wiring, sender and gauge. Hope to get to it this weekend. Will be trying all suggestions. Thanks for all the input.

 

[JUST-IN-TIME]

they have problems with gauges and sending units

they know about it, but deny it everytime

 

[BobP]

?? So what happened?

 

[cdwood]

Got pressed for time, opted to fish first. Then noticed later that my starboard thru hull for the deck drain was grenading, had to tend to that.

 

[cdwood]

Alright, checked all grounds, everything in place including common bus for both batteries.

I think what I did here was take both leads from sender right to the gauge.

So my question is how does the sender get it's power? Should there be 12v at the sender somewhere?

Here's what I do have:

12v to the gauge with key on.

5.6v out of gauge to sender, verified.

All grounds are good.

When key is turned to on the needle does bump a little, the gauge lite comes on but the gauge still reads as empty.

Really at a loss here.

 

[cdwood]

ttt

 

[JUST-IN-TIME]

turn key on

then ground out the gauges sender unit


it should read full

if it does then sender or wires are bad

 

[cdwood]

Can get the gauge to read full by shorting the leads.

Also get an Ohm reading of 90 ish which would indicate the sender is working correctly, tank is almost full.

 

[rmajor]

Similar Sender Problem

Had a similar problem. Had new wiring, new sender, new gauge, clean tank. Gauge worked, but read near empty. Ended up that sender float was hitting baffle in tank. It hit because I rotated the sender unit to make the holes line up. Didn't remember about the location of the baffle. Twisted float a little, and worked great.