I give up ( gas gauge ) {FIXED}

[Jeff-in-PA]

I've been trying to get my gas guage working in my pontoon. I replaced the gas guage itself, the sending unit and checked the wiring for continuity.

I've decided that I will run brand new wires and hook it up to the switch panel where you turn on the various electrical components. ( when I turn the main switch on, the gas guage will "work" )

What I would like is a simple explaination of the wiring. I have a same guage red and black wire run under the console to the sending unit. If I need another wire run, I will do that.

Thanks
Jeff

 

[Bondo]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

Ayuh,... There's a Power wire to hook to the (+) post of the Gauge, along with it's ground, if so equiped...
The Sender terminal of the gauge is wired to the big center post on the sending unit...
Then the sending unit will have another wire going to ground....

If you touch a ground to the big terminal in the center of the sending unit, the gauge should Peg to full...

 

[stylesabu]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

gas gauges are pretty simple. if you follow what bond-o said gauge should peg. if it doesn't trying grouding sender lead at gauge, if this doesn't get any responce double check power and ground it gauge, if all is right gauge is bad

 

[Silvertip]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

Here ya go.

So you have quickly learned that simply replacing parts is not the solution to a problem. You first "diagnose" then "replace" or "repair" as required. The simplest test of the system you have is to ground the send terminal either at the gauge or at the sender. If the needle pegs that much of the system is good. If not, look for +12 volts on the "I" terminal. If present, make sure the ground terminal has a good ground. Sender resistance should read 240 ohms (empty tank), 109 ohms (1/2 tank) and 33 ohms (full tank) give or take a bit. You must measure resistance with the sender lead disconnected.

 

[Jeff-in-PA]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

We untarped the boat today so I could actually get into it.

With the key in "on/run" position, if I jump the the sender wire to the ground, the guage immediately pegs to the full position.

I checked from the power wire ( "I" ) to ground and have 12.75 volts.

Since I have another set of wires run, I hooked up a different wire for the sending unit. No change ( the guage doesn't work and yes, I did hook up both ends. One end to sending unit and the other to the guage at the "S" terminal. I have switched them back. )

With the key in the "on" position and my meter set for DC voltage in the 20 range, I have 3.5 volts from the sending unit itself to the ground on the sending unit.

With the key off and the sending wire disconnected, I get a reading of 119 ohms which would be correct since I have about half a tank of gas.

What should I check next?

Also, thank you very much for help and especially with your patience.

Jeff

 

[Silvertip]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

The ground from the sending unit to the boat ground (battery negatigve.) Follow my diagram. Mark the points you checked and check those you didn't.

 

[Jeff-in-PA]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

The ground from the sending unit to the boat ground (battery negatigve.) Follow my diagram. Mark the points you checked and check those you didn't.

Thank you.

 

[stylesabu]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

so all's well?

 

[Jeff-in-PA]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

Here ya go.

OK, I am thoroughly confused now. With the key on, when I connect my volt meter ( 20VDC range ) in between the ground wire on the sending unit and the ground tab itself, I get a reading of 13 volts

The purplish wire in your diagram is the one to the center of the sending unit and I put my meter in between the black ground wire which connects on a tab by one of the outer screws.

Is this correct or did the previous owner wire something incorrectly?

 

[Lyle29464]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

1 The 13 volts is normal and it tells you your sender wire is good.
2 hook everything back up.
3 run a ground from your battery to the middle of the sender on the tank
If you get a full reading your sender is bad or its not grounded.

4. leave the ground wire on the battery and move it from the middle of the sender to the ground on the sender. If you get a correct reading at the dash your ground is bad between the sender and the battery.

 

[Jeff-in-PA]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

1 The 13 volts is normal and it tells you your sender wire is good.
2 hook everything back up.
3 run a ground from your battery to the middle of the sender on the tank
If you get a full reading your sender is bad or its not grounded.

4. leave the ground wire on the battery and move it from the middle of the sender to the ground on the sender. If you get a correct reading at the dash your ground is bad between the sender and the battery.

1. check

2. done

3. I ran jumper cable from negative post on the battery to the gas tank/sending unit ( I had a short piece of 12 guage wire clamped into the end of the jumper cable).
With the key on, the fuel guage jumped to FULL.

4. When I touched the jumper wire to the grounding plate I GOT SPARKS

The gas guage moved to just over empty but I wasn't exactly too thrilled about making sparks on the sending unit of my gas tank. The original wiring is all hooked up. A green wire and a black wire hook up on the post /mounting plate. The green wire goes to the side where the fill is and the black wire snakes it way under the boat to the console.

I double checked to verify that I was hooked up to the negative post of the battery.

I have the battery disconnected right now as I think that I was a serious wiring problem. From my extremely limited knowledge of electricity, I don't think there should be any sparks on a ground.

Here's what I "think" I should do next. Disconnect the factory black wire at both the sending unit and the guage in the console.

Run a new green wire from the sending unit mount tab to the fill plate.

Using a new black wire ( same guage ), run from the ground tab of the sending unit to the console where all the negative terminals are located.

Run another black wire from that same negative black to the guage.

Does that sound correct? That would give me the same wiring as the diagram that Silvertip posted. ( right? )

Thanks again everyone.
Jeff

 

[Silvertip]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )

No! You are getting yourself all wrapped around the axle. Why on earth would you run a ground wire from the shell of the sending unit all the way to the console and back again when the sender is just a foot or so away from the battery to start with. You are not thinking logically here. If the other gauges work, the ground on any of those gauges is exactly the same as connecting to the negative terminal of the battery. Hence, connect ground on the gauge to ground on any other gauge or the ground buss at the helm. If the other gauges work then there must be +12 volts present at them when the key is in the RUN position. So then make sure the +12 volt terminal (sometimes marked "I") on the fuel gauge is connected to the +12 volt ("I") terminal on any other gauge. Now then, you admit limited electrical knowledge so I suspect you are not using an ohm meter correctly. So here ya go. Disconnect what you THINK is the send wire at the "S" terminal on the gauge. Set you meter to any scale that can read 240 ohm (probably the 1K scale). Touch the positive probe to the end of the send wire, and touch the negative probe to ground. If the send wire is correct and sender is wired properly you should have a reading as follows:
full tank = 33 ohms. 1/2 tank = 109 ohms (roughly) and empty = 240 ohms. You can do the math if you know roughly how much fuel is in the tank. If you get no reading, touch the probes together and the meter should go to zero indicating it is working. If not, the meter is not functioning. If you still get confusing results, incorrect results or no results (at least that you can make sense of), you have bad sensor wiring. So next, measure resistance from the shell of the sender to the negative post of the battery. Should be zero. If not, connect the ground wire properly. Lastly, the reason you got sparks in your test is because you completed the circuit much like actuating a switch. Just follow the diagram.

 

[Jeff-in-PA]

Re: I give up ( gas gauge )

Re: I give up ( gas gauge )



My gas tank is under the lifted cover. My battery is all the way in the back on the starboard side.

~~~~~~~~~~~

I started out by checking the ohm readout of the original sending unit. I would get erratic reading ( ex. when it was at half tank position, the reading would fluctuate between 90 -130 ohm )

So here's what I did. I unplugged the factory wiring at the gas tank sending unit. I ran a new wire from that tab to the plate on the side where the gas tank fill is located.

( pinkish wire by the black hoses )

At the gas gauge itself, I disconnect the factory ground wire and attached another black wire which I connected to the ground block.

When I turned on the key, it worked

Silvertip, thank you very much for your help and especially for your patience.
Thanks to all who helped with suggestions.

Jeff