Re: Yamaha Oil System
There are several kinds of fuel gauges out there.(balancing coil, zeroed balancing coil, heated coil and digital.)<br /><br />With all types, the gauge requires the sending unit (tank sensor) to complete a ground circuit. Gauges and tank sending units can be check for resistance, but the reading may not mean much to you if you don’t have a spec for the resistance value. Generally, an open in the gauge or sender means trouble.<br /><br />Things to consider when troubleshooting gauges of all kinds:<br /><br />>Supportive wiring and voltages (power, ground, sender lead, lighting)<br />>The sending unit or sensor<br />>The gauge itself<br /><br />The easiest way to check the gauge is to give it what it needs, and if it doesn’t function, pitch it.<br /><br />>Using a test-light or voltmeter, check to see if the gauge is getting power with the key on. Since you probably don’t know which one is power, just use a process of elimination and check all wires at gauge. One of them should read battery voltage with key on, and zero voltage with key off.(be sure to ground the voltmeter or test-light to a good ground)Some old gauges required 5 volts, but I think your vintage of motor suggests a newer boat.<br /><br />>Using a test-light or voltmeter, check the ground terminal. It should have no voltage when checked with key on and lights on. Connect the black lead of voltmeter or test-light to a known good ground, and with the red lead or probe, check the ground lead.<br /><br />>The sending unit lead will be the one going to the tank. The best way to check the sender circuit is to disconnect the lead at the tank and watch for a change in gauge readings.(key in on position)<br /><br />>Remove the tank sender lead, and pending on type of gauge, the needle on gauge should go to empty or full, nothing in-between. <br /><br />>Ground the sender lead with a test-light (if you ground some types of gauges without test-light, damage occurs) You should see the gauge move to empty or full, pending on gauge type. The key here is you should see it move when grounding or un-grounding.<br /><br />>If there is no needle movement, go to the gauge and disconnect the sender lead. Ground the sender terminal with test-light and observe the gauge. <br /><br />*if the gauge is getting:<br />>12 volts with key on<br />>Good ground on ground terminal<br />>No movement on gauge with test-light installed (grounding the sender terminal) then the gauge is bad<br /><br />*If the gauge responds to the test-light, the sender, wiring to sender or tank ground is bad.<br /><br />You can measure the tank sending unit as shown, but the reading won’t mean much to you because you don’t know what position the float is in. The proper way of testing the sender is to remove it and check its resistance at the full, empty and half position and compare to spec. You do know one thing, the reading should not be high (1200 ohm or up) or open circuit. If it is, you’ve found the problem.<br /><br />*Again process of elimination will work. If grounding the sender lead at the tank moves the gauge, and you’re sure the sender ground is good…….sender is bad.<br /><br />*most common failures<br />>worn or corroded tank sender<br />>bad tank sender ground<br />>no power to gauge (fuse)<br /><br />If this doesn’t help, measure the voltages at each terminal of the fuel gauge with a digital volt meter and get back to us with the readings……<br /><br />
