79 fuel gauge

[rizzo4u2]

whats up with theses gauges somtime they work, sometime they dont, cleaned all the terminals on the bike, replaced the sending unit, replaced the fuelgauge unit, i guess the problem is lying in the gauge itself, any ideas

[planedick]

I've discovered

Battery condition has a lot to do with the fuel guage. A battery that is old and only shows 12 volts when off will make the guage only work when on the freeway when the RPM's are high for extended periods of time and then probably a lesser reading than actual amounts of gas. There is a little device in the tach that reduces the voltage for the guage and the voltage should be 7 volts exactly. Anything less and it won't work right. Good test is to put your battery charger on the bike with at least 2 amps charge rate and when the battery reads at least 13.4 volts turn it on and see if it works right then. Be sure the voltage stays up for the test by being sure the headlight is off for the test.

[rizzo4u2]

the battery is at full charge, when the bike is not on the road, the gauge moved up slightley and then fell for like a couple of seconds ,all connections are clean and the right amount of current is getting to the gauge, i guess it could be the gauge itself