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Discussion Starter · #1 ·
Hi All, I have a 77' Islander 32 and the gas gauge lights up but the needle doesn't move, even after I fill the tank. My question is: could this be the sensor in the tank, and if so, where would it be located on the tank/what would it look like? I'm assuming its an older float type sensor since it looks like the original tank, and it would have to have a wire going to it, right?

I plan on tracing the wires from the gauge to the box but the gauge light is working so it has to have juice going to it. And it looks like a new gauge compared to the others on the panel.

Just bought this and didn't notice the gauge issue earlier.

Thanks for yer help!
 

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The light behind the gauge could easily be on a different cct than the gauge itself.. you wouldn't need the light in daylight so I'd guess all your gauge lighting is on another cct.

Could be as simple as a loose wire at the gauge or at the tank too... (independent of the lamp)
 
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I found this some where and used it to test my gauges.

Test Procedure For Fuel Gauges Used By Catalina Yachts
There are four components in the fuel gauge system on Catalina Yachts and therefore four possible sources of fuel gauge problems:
1) The fuel gauge in the engine control panel may be defective.
Test procedure: Disconnect the pink sender wire from “S” (sender) terminal on gauge. Turn on the ignition switch. Pointer must deflect to extreme left. By temporarily shorting together the “S” and the “G” (ground) studs, pointer must deflect to the extreme right. Re-connect the pink sender wire to the gauge after the test.
2) The pink sender wire may be disconnected from the sending unit at the tank or shorted to ground.
Test procedure: Disconnect pink sender wire from terminal on sending unit in Tank. Attach pink wire to a known ground, such as engine block or battery negative. Do not assume that fuel tank is grounded. Turn on ignition switch. Pointer must deflect to extreme right, as in previous test. Disconnect pink wire from ground. If pointer still deflects to extreme right, pink wire is grounded at some point between the sender and gauge. Check all connection points on pink wire or replace the entire wire.
3) The black ground wire may be disconnected from the sending unit at the tank or not grounded at the other end.
Test procedure: If the gauge tests “good” and pink wire tests “good” attach pink wire to the black ground wire on the sending unit at the tank. If pointer does not deflect to right (as in test above) the black wire is not grounded. Follow the black wire from the sending unit in the tank and make sure it eventually connects to ground.
4) The sending unit in the tank may be defective or the wrong unit may have been installed.
Test procedure: If the gauge tests “good”, the pink wire test “good”, and the black ground wire tests “good” the sending unit in the tank is defective or the wrong unit may have been installed. The specifications of the correct sending unit are: Stewart Warner, 240 to 33 ohms resistance. There are several other resistance specifications available but those sending units will not work in this application.
 

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Discussion Starter · #4 ·
Thanks you guys! I checked it today and there is power going to all four connections in the back of the gauge and at the sensor itself. Gonna try olddog60's test procedure on it next. I should have made note of the gauge manufacturer but didn't :( Noticed quite a bit of corrosion back there too so a good cleanup and tightening is in order.

I did notice a small rectangular part free of the panel but in the overall circuit that had "15A" on it, and I'm assuming this is an in line fuse; it had power only on one side. This may be the culprit but will have to map out the schematics for this further. Everything else on the panel works tho...
 

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A picture would help, but I'll go out on a limb and say that the rectangle thing is supposed to hold a fuse. Put one in and you'll have power to both sides - and to the sending unit.
 

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Do ANY of the gauges work? I am having trouble imagining that only the fuel gauge is protected by a fuse...

On my boat there is an ATM 20 fuse, which goes to the key switch.

One of my pet peeves lately has been with owners that do not have an up to date schematic of their boat's primary electrical system. Here is a recent copy of mine that you can use as an example (I'm not saying it is a good example, just an example);


I created this in PPT, and update this as frequently as I make changes, such as changing a fuse type or rewiring the batteries.
 
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Discussion Starter · #7 ·
I tried to take a pic but my crappy phone doesn't have flash and the pen light didn't do anything..and btw all the gauges work, even the gas gauge lights up as previously mentioned, the needle just doesn't work.
@eherlihy..thanks for the schematic..I've been looking for an Islander specific one to no avail and have resigned myself to starting one from scratch, so your pic will be helpful.
My next step is to replace that fuse and see what happens, just don't get that that fuse would be dedicated to one part of one gauge (since everything else works). The joy of boat ownership!
 

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95% of the time it will be the sender. Check the resistance of the sender at the fuel tank. 240 to 30 for American and 30 to 0 for EU.
 

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And while you're at it, next year start to take measurements of engine hours and fuel consumption. Once you KNOW the fuel use, you'll rely less on the stupid gauge.
 

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Discussion Starter · #10 ·
Update: Well, I did the tests provided by olddog60 (thanks again!) and it turned out to be the sending unit after all, its ordered and on the way.
 

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The fuel gage sending unit in the tank is a variable resistor. The manufacturer can give you the specs. For example I have a Moeller unit. For these units you can test the unit by using a meter set on ohms at the lowest setting. Using the positive on the center post of the unit, at the top of the tank, and the negative on the ground you should have a reading of approximately 33 ohms in the full position and approximately 240 ohms in the empty position. This resistance range is a common one for fuel gages.
 
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