Fuel gage question.

[81_chapparel194]

My fuel gage isn't working i have 6 wires coming off the back of gage. One red one black going to sending unit. One hot and ground going to gage light. One wire going to the fill neck. Assuming this is a ground. The sixth wire appears to be another ground. Does this sound right? How does power get frOm unit to the gage?

 

[jayhanig]

Re: Fuel gage question.

This ought to help. You need to run that last wire to a 12 volt source off your ignition switch so the gauge is only powered when the engine is running.

 

[Augoose]

Re: Fuel gage question.

Power should not be at the sending unit itself - its only a resistance reading. The gauge, which is powered by "ignition" only or is referred to as "switched power" as jayhanig said, reads the amount of resistance coming from the sending unit which is controlled by the amount of fuel in the tank. You'll typically have a lead going from the sending unit to the gauge and back to the sending unit, a ground for the sending unit, another ground for the gauge as the gauge likely doesn't ground through the case, and then power to the gauge. Then as you've already identified a ground and hot lead for the lamp in the gauge itself.

 

[81_chapparel194]

Re: Fuel gage question.

Power should not be at the sending unit itself - its only a resistance reading. The gauge, which is powered by "ignition" only or is referred to as "switched power" as jayhanig said, reads the amount of resistance coming from the sending unit which is controlled by the amount of fuel in the tank. You'll typically have a lead going from the sending unit to the gauge and back to the sending unit, a ground for the sending unit, another ground for the gauge as the gauge likely doesn't ground through the case, and then power to the gauge. Then as you've already identified a ground and hot lead for the lamp in the gauge itself.

There is only a single wire from gauge to sending unit. And a ground on sending unit.

 

[Augoose]

Re: Fuel gage question.

There is only a single wire from gauge to sending unit. And a ground on sending unit.

Sorry - didn't mean it that way - a single lead to the sending unit is correct

 

[glenn property of pam]

Re: Fuel gage question.

there should be 5 wires at the gauge and 2 at the sender.
the gauge is +12v, -12v, sender, light 12v+, light 12v- there maybe wires connected on the + and - to other gauges.

at the sender you have sender, ground, and on some boats theres a extra ground especially if you have a metal tank or a metal filler cap.


http://forums.iboats.com/showthread.php?t=225399 this link may help.

think of the gauge like a light bulb you hook the light up to the positive then the other side goes to the sender. the sender controls how much current goes to ground so as the sender moves the light gets brighter or duller.

 

[81_chapparel194]

Re: Fuel gage question.

The needle goes up to empty from bottomed out. If i stick my test light to the sending unit wire going to the gauge it goes up to 3/4 of a tank. I wonder if my float is stuck in the empty position? I tried to take the sending unit out of the tank but one of the screw heads stripped so I have to figure how to remove the screw. I have to replace the gasket anyway it's leaking. Any suggestions on the incorrect level reading?

 

[sschefer]

Re: Fuel gage question.

Up to empty is what you'll get if everything but the sender is connected to the gauge. To see if your sender is stuck, you first disconnect the wires on the sender (the center one and the ground) then check the resistance from the center pole on the sender to ground. The resistance range is 35-200 ohms so anything above 35 and you got gas.

The normal ABYC wiring is

Purple = Key on Accesories - Goes to gauge 12v+
Black = negative (commonly refered to as ground) - Goes to 12v- on the gauge.
Black from outer ring of sender - Goes to any 12v- source but often it's brought all the way back to the gauge and put on the 12v- post.
Green - Ground from filler cap metal to 12v- at the sender or all the way back to the gauge 12v-
Blue - Lighting circuit.
Black - 12v- to other gauges - Usually setup in a daisy chain fashion. The Purple and the Blue may also be chained to other gauges.
Pink (might be red) goes to the S terminal on the gauge and the center terminal on the sender. These are often replaced with red wire because pink is hard to find. Red usually indicates that the wire is 12v+ battery but in this case it's actually in series in the circuit. It will indicate 12v to ground when the key is on but it's not 12v+ from the battery. That may be what's got you confused.