Gas Gauge

lcochrane

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I have a 1990 Sea Ray with a 5.0LX Mercruiser Alpha One. I had some trouble with my gas gauge a while back and bought a new transducer, level indicatar (I think that is what it is called, the thing in the tank). It never really seemed to work last year, so I took it out this year and measured the resistance, it showed -15 hooking it up one way and open, I think that is what it is called screen went blank and didn't show any numbers the other way. I just bought it last year, is it bad already. Any thoughts? The gauge still doesn't work.
 

alldodge

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With the sender out you need to measure the resistance in ohms. The measurement should be taken from the single terminal and the flange. Is your sender an arm type or tube type?

To check the gauge, turn key ON, then ground the sender wire to the tank. This should peg the gauge full
 

wrench 3

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Make sure that you disconnect the wires from the sender unit before testing the resistance. I don't know exactly what the resistance should be but if it moves smoothly from high to low when the float is moved up and down, it should be OK.
If it test open (Infinite resistance, usually a flashing "I" on the display) still run the test on the gauge. 12V to the sender will burn out a new sender in short order.
 

Silvertip

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Looks like you were "intending" to measure "resistance" (ohms) but had the circuit powered (key on) and were actually measuring voltage with the probes reversed. You cannot measure resistance with power on (the meter supplies power in "resistance" mode) or with anything else in the circuit. The first step in electrical troubleshooting is to understand how to properly use a meter. If you were indeed measuring voltage at the sender you had the probes reversed and the meter is reading incorrectly as a battery produces 12.6 volts depending on state of charge.
 

lcochrane

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Thank you for all the input, I know more now and see what I can find out. It is an arm type.
 

lcochrane

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I pulled out the sender and measured resistance, it varied as I moved the arm up and down, so I don't think it is the sender. With the power off, should I be able to read resistance at the gauge? and should it be the same as the resistance measured at the sender?
 

alldodge

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I pulled out the sender and measured resistance, it varied as I moved the arm up and down, so I don't think it is the sender. With the power off, should I be able to read resistance at the gauge? and should it be the same as the resistance measured at the sender?

Don't measure resistance at the gauge. To test the gauge, turn key ON and check for 12V on the purple wire.
If you have 12V on the purple wire, find the pink wire also on the gauge.
Jumper a wire from the pink wire to ground (the black wires). This should cause the gauge to peg Full
If gauge pegs Full with 12V on purple wire and jumper on pink the gauge is working.

If gauge is working next jump the wire at the sender to ground, this should peg the gauge also.
 

lcochrane

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AllDodge


​I actually did the last sentence on accident and the gauge went beyond the full line and it is resting on the bezel edge, any thoughts? I adjusted the sender arm to fit the tank, it is a universal sender, I don't know if there is anything else physical that I can do.
 

alldodge

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OK, key ON and jump at tank to ground you now know the gauge is OK.
Remove the sender, connect the pink wire to the gauge, touch the side of the sender to the side of the tank. Turn the key ON and move the arm up and down. The gauge should move. If it does not, connect another ground wire from the engine block to the side of the sender and try again. If it still does not work let us know what is the part number of the sender
 

wrench 3

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Is there any chance that the float is getting stuck on something, like the side of the tank or the fuel pick up tube?
 

lcochrane

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AllDodge,

​Ok so I did the first part quickly and gauge did not move. Have not had a chance to try second part yet. I bought a Moeller 035725-10 electric fuel sender. I hope this information helps
 

alldodge

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Moeller 035725-10

Yep that tells me you have the correct sender. It's 240 to 33 ohm (240 empty to 33 full)

but since it did not move when you ground the pink wire, you need to try it at the gauge. If it works at the gauge then its either the pink wire or a ground to the tank
 

lcochrane

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This may be a dumb question, but what do mean by try it at the gauge? I looked behind the dash and the gauge has like 6 wires on it omg. I don't know if that is normal. Also, is there any way to remove gauge and pull wires through to the front. Do you just unscrew the bezel from the front?
 

alldodge

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This may be a dumb question, but what do mean by try it at the gauge? I looked behind the dash and the gauge has like 6 wires on it omg. I don't know if that is normal. Also, is there any way to remove gauge and pull wires through to the front. Do you just unscrew the bezel from the front?

Most of the wires are doubles, if not triples. You should have a purple coming in and a purple going out to the next spot. You should also have a black going in and back out. There will also be a wire used for turning on the lights in the gauge and going back out. The wire your looking for if it has not been changed is a pink wire on the S terminal. This wire should be the same color as the wire on the tank sender, since this should be one solid wire.

yes the gauge can be removed, but (there is always a but) we would need some pics to see how to remove it. That said, I don't think it needs to be removed, just needs to understand what your looking at.

This is the standard wiring for the typical gas gauge. Note this wiring shows that the lights will light up when the key is turned, in many cases theis is controlled by another switch on the helm. Also note this shows a white wire for power where Merc uses Purple

Gas Gauge.jpg
 

wrench 3

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Two things:
If I understand post #9 correctly, you accidentally grounded the pink wire at the tank and the gauge pegged to full. If so, the wiring to the gauge is OK and the gauge worked.
You said that the gauge "is" all the way to the bezel past full. With the key on and the pink wire disconnected it should return to empty. If it didn't, tap on the gauge with your knuckle and see if you can dislodge it.
 
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