Bouncing Fuel gauge

One of two things. Lose wire connection or the sending unit is about to give up.

 

HM..... that would be it.

You best get to it. Figures a 300 gallon tank, 150's on each one, 120 stated remaining, 60 per tank. Less than half but above 1/3. Eh... that is not much to slosh the gauge unless you hit a real bad washboard...

 

something could have broke loose in tank, like part of a baffle & is hitting the metal rod with float in tank. mine has been doing that for 15 years.

 

Agree...It is rarely the gauge itself but most likely a bad connection or the sending unit is bad.
All it does is work on ohm readings from the sending unit..

 

Most likely a sending unit. Typically not too difficult to change out.. I've replaced them on T800s, T660s, and T680s... unfortunately, if I ever did one on a T700, I don't remember it. The T680, you can reach it underneath the back of the cab.. pretty simple to swap them out. The T660, we'd have to remove the cab fairings, loosen the tank straps, disconnect the supply and return lines, and rotate the tank (much easier on a near empty tank, suffice to say). I would expect the T700 to be more like the T680 in this regard, but I can't promise it.

 

My 09 Columbia did that till I replaced the sending unit.

 

It's just six screws. Not really a lot to it if you don't have to take off the fairings and rotate the fuel tank. I wish I could tell you definitively which is the case, but I've only ever worked on T700s a couple times (there were a couple in a fleet of primarily T660s, then the T680 became the mainstay of said fleet), and that's one repair I've just never had do on that particular model.