Gas gauge quit working on S model

[nvr2old]

The gas gauge on my '79 S has stopped working. After I finished the build it worked fine, then after a month or so it only registered a half tank when filled, then down to a quarter, now..nothing at all. I've checked all the external electrical connections and they seem fine..do I remove the sending unit next..? If so, what do I check for? Thanks for any advice.

[Steve]

I've checked all the external electrical connections and they seem fine..do I remove the sending unit next..?

Yes.

If so, what do I check for?

Check for a good Internet connection to BassCliff's Little Website and grab a copy of the Fuel Gauge Send Unit Repair document.

Remember, ... that "little website" is not just for newbies.

.

[nvr2old]

Even an old-timer needs to be reminded of the vast amount of documented help on this site. Thanks for pointing me in that direction, Steve.

[posplayr]

I have a similar problem on mine; the PCB board wire wound slider pot that makes up the gauge is fabricated using a piece of Formica of similar board. It tends to warp and throw the slider off. I have to get into mine. It just goes bonkers with just the key on.

[Nessism]

Bimetal (needle moving) component in the gauge is known to fail on occasion too. Sender unit failure is more common though, and easier to fix, so I'd look there first.

[rustybronco]

I'll go with disconnecting the two leads at the tank sender and check the float's (senders) resistance to confirm.

[Steve]

I'll go with disconnecting the two leads at the tank sender and check the float's (senders) resistance to confirm.

Yes, that can work both ways, too. Ohm out the leads to the tank to check the sending unit, or jumper across the two on the bike to watch the gauge go to FULL.

Just keep in mind that if the sending unit is really wonky, you won't know whether your readings on the meter are correct or not.

.

[Joe Nardy]

Jethro did a very nice writeup about cleaning up the fuel sending unit. Here's the link. It was years ago and the pics are no longer visible but maybe he can re-post them for you.

Thanks,
Joe

[nvr2old]

Thanks for all the quick replies, you guys. I'm such a squid when it comes to electrical problems..not even sure how to use a multi-meter as embarrassing as that is to admit, but I'll pull the sending unit and make sure all the components are working correctly and go from there. Love this site.

[rustybronco]

then after a month or so it only registered a half tank when filled, then down to a quarter, now..nothing at all.

It's either going to show resistance, or it isn't. It's a pretty cut and dried senario.

[xxBenJamminxx]

I have just the opposite problem. Gauge was on about a 1/3 of a tank when I got it. Did some poking around in the wires working on the directionals and it went to full and since has only dropped about a needles width under full no matter how much gas is in it. Gonna have ohm test the tank side myself now that I have a new multimeter but what can I test on the gauge side to see if that is even getting power at all? I have tried testing the different leads that go into the back of it with no results (but that was just before I found out my old multimeter was junk.)

[posplayr]

I have just the opposite problem. Gauge was on about a 1/3 of a tank when I got it. Did some poking around in the wires working on the directionals and it went to full and since has only dropped about a needles width under full no matter how much gas is in it. Gonna have ohm test the tank side myself now that I have a new multimeter but what can I test on the gauge side to see if that is even getting power at all? I have tried testing the different leads that go into the back of it with no results (but that was just before I found out my old multimeter was junk.)

look at the manual it pretty much explains how to test the sensing units.

[hampshirehog]

The initial easy check is to put 12 volts through the meter first (just unplug the sender and connect up the wires going to the meter to your battery). If the meter shoots up to full it's your sender that's at fault. If it doesn't move your problem lies in the wiring or the meter.

[xxBenJamminxx]

The initial easy check is to put 12 volts through the meter first (just unplug the sender and connect up the wires going to the meter to your battery). If the meter shoots up to full it's your sender that's at fault. If it doesn't move your problem lies in the wiring or the meter.

What if it always shows full even with it unplugged?

[Agemax]

What if it always shows full even with it unplugged?

then the meter is knackered..........