Fuel gauge needle doesn't move -- '97 PS 190

[TallSkinnyGuy]

My fuel gauge worked great all last season. After winterizing the boat in November I stopped by a gas station to fill up the tank and I turned the key to the "on" position so I could watch the needle go up as I filled it. I had a half tank of gas, but the needle didn't move. Just stayed below the Empty mark.

In the past I've had trouble with the sending unit and the needle would jump to the same position on the gauge regardless of how much fuel was in the tank. I fixed that problem by re-gluing the magnets back to the float. I pulled the sending unit out of the tank this morning and everything looks fine. Float slides freely, magnets in place, no corrosion. I turned the key on and touched the two leads directly together and the needle still didn't move.

I pulled out my multimeter, but I really don't know how to use that thing. I made a guess on the settings and touched it to the sending unit wires and the multimeter displayed some numbers, which causes me to think there is current flowing through the sending unit.

Would I be correct to assume this problem is likely the fuel gauge not responding to the sending unit? If so, do I need to replace the fuel gauge or is there a potential fix?

[TallSkinnyGuy]

So I was able to figure out the multimeter tonight and tested the sending unit. It had the right amount of ohms at empty and full, so the problem appears to not be the sending unit. Can anyone describe or point me to a thread that describes how to test the wires and the gauge?

[Flexx]

Hey Bro,
look at this Thread Post #4 and #13.
https://www.mastercraft.com/teamtalk...=gauges&page=2

I had the Troubleshooting guide on my old Laptop wich is burned…

[Flexx]

Oh, found the TS-Guide on my hard Disc!

If you give me you Mail, i will send you the Guide as PDF

[ahhudgins]

I apologize if I'm incorrect, but if you just have a two-wire sending unit, then the only other part of the system is the gauge. I repaired my sending unit in 2013 and it's still working. I made several notes in this thread. Read all pages.
If you jumper across the sending unit with key in the RUN position, the gauge should go to FULL.

https://www.mastercraft.com/teamtalk...ad.php?t=56610

[TallSkinnyGuy]

I found another tutorial that told me to test that 12 volts was coming to the back of the gauge. The battery is producing 12.5 volts, but nothing is getting to the gauge, so it looks like I have an ignition circuit problem. I assume I should be able to confirm that by connecting the battery directly to the gauge and see if that kicks the needle up.

[TallSkinnyGuy]

I apologize if I'm incorrect, but if you just have a two-wire sending unit, then the only other part of the system is the gauge. I repaired my sending unit in 2013 and it's still working. I made several notes in this thread. Read all pages.
If you jumper across the sending unit with key in the RUN position, the gauge should go to FULL.

https://www.mastercraft.com/teamtalk...ad.php?t=56610

Turns out the gauge needs power to work and that appears to be my problem. I had tried what you suggested with the jumper across the sending unit posts, but my needle still didn't move. So, there are actually three parts of the system when you include the power source (including power source connections).

[Andyg]

Your fuel gauge works by having a float that slides up and down in the tube that has a magnet on it. Most of the time on this version the issue is the magnet has come out of the float and stuck to the sensor so the fuel gauge is stuck at whatever level that is at. The fix is to get the magnet out and put it back into the float and us JB weld to keep the magnet in place. I did this to my 190 back in 2000 and it was still operational as of 2017.

[Andyg]

Here is a thread about it.

https://www.mastercraft.com/teamtalk...ad.php?t=56610

[ahhudgins]

Turns out the gauge needs power to work and that appears to be my problem. I had tried what you suggested with the jumper across the sending unit posts, but my needle still didn't move. So, there are actually three parts of the system when you include the power source (including power source connections).

Yeah, I wasn't going to include the wires, voltage, and ground as "components". The link that I posted was from when I repaired my sending unit a few years ago. There is a ground post on the gauge that is just for the light bulb, and the other two larger posts are what works the gauge. One of the large posts will have 12V when the key is in the RUN position, and the second large post runs back to the sending unit. 99.9% of the time the wire that has the 12V from the ignition circuit is the purple wire....but these boats have a ton of splices behind the dash.

[TallSkinnyGuy]

My gauge has a connector for the light, a ground post, a sending unit post and an ignition post. They are all labeled and therefore easy to identify. When the key is in the "on" position I believe I should be getting 12V when I connect my multimeter to the ground and the ignition post. Strangely, my meter actually shows negative voltage when I do this. I don't know what that means, but from what I've read, it at least means that I'm not getting power to the gauge, which would explain why the needle doesn't budge. I guess at this point I need to determine if the problem is with the ground or with the ignition wire. Any directions on the best way to do that would be appreciated.

[ahhudgins]

Keep it simple. Put your negative meter lead on the negative battery post and leave it there. Put your positive lead on the positive battery post and make sure you have +12V. If it’s negative 12V you have your leads backwards in the meter. Don’t laugh…I see it at work all the time. The ground post on the gauge is just for the bulb.

If your meter leads and battery check good for +12V, just leave your negative lead on the battery and move your positive lead along the path from the battery. Ignition switch to the RUN position. +12V should be out on the IGN post of the ignition switch and out on the purple wire to the ignition circuit and all of the gauges. Have you checked to see if the fuel gauge is the only one not working? I replaced a dash in an 87 Prostar for a friend and the wiring was a mess. There were black and purple wires spliced together and I could touch the splices and his gauges would fluctuate.

[88 PS190]

I like to be even simpler. A functional gauge should peg to full if you disconnect the wire from the sending unit. You can usually get to the sender faster than the gauge.

If it pegs when you remove it and then goes to zero when you connect it there is a bad sending unit.

If it doesn't move when you disconnect it you have to go upstream.

[ahhudgins]

I like to be even simpler. A functional gauge should peg to full if you disconnect the wire from the sending unit. You can usually get to the sender faster than the gauge.

If it pegs when you remove it and then goes to zero when you connect it there is a bad sending unit.

If it doesn't move when you disconnect it you have to go upstream.

He has already jumpered across the sending unit and got no response at the gauge. He says that he is missing 12V at the gauge....depending on his use of the meter.

Actually you have it backwards. If you remove the wire at the sending unit, it's an open circuit and the gauge stays at empty (no current flows through the gauge). If you jumper across the sending unit it puts ground on that side of the gauge and it pegs to full on (full current through the gauge). That holds true as long as the key is in the RUN position and 12V is applied to the gauge, and the ground wire is good at the gauge.

[TallSkinnyGuy]

Thanks guys. I have a list of tests to do this weekend to narrow down the power problem.