[racerx23]

75 transam fuel gauge is pegged all the way past the full mark. Does this sound like a sending unit or a ground wire situation or other ???
Thanks in advance.

[Peter Serio]

That gauge has power and it needs a ground at the dash cluster. If you have the trans am dash with the tach and the clock then the fuel gauge is over towards the center of the dash in a separate pod along with a volt gauge.

The ground is via a plug in wire at back of the voltage gauge.

The tan wire runs from the back of the gauge to the tank sender. If the gauge has power and ground but the tan wire is broken or un-plugged then the pointer will go all the way over to the full line and beyond. A bad sender could also be the "open" And a bad plug-in connection at the body harness could also cause this problem. Same deal with the plug-in at the trunk area.

[74Bluebird]

My 74 did that and it was the sending unit gone bad. Replaced it and worked fine.

[njsteve]

Originally Posted by 74Bluebird

My 74 did that and it was the sending unit gone bad. Replaced it and worked fine.

Same here. They don't make a 75 sending unit but the 76 and up (Spectra FG103C) works fine. The metal line that comes off it has a 90 degree turn at the end. Cut the 90 degree off and flare the end and you've got an exact duplicate of the 75.

See here: http://forums.maxperformanceinc.com/...44#post5486544

[Peter Serio]

Very common for the sending unit to go bad, over time they corrode and given the many other ingredients which are mixed in and sold as "Gasoline" today those additives are not very friendly to the sender! Electricity, copper and metal with a nylon plastic strainer "sock" on the end of the pick-up tube. All of the old senders I have pulled out of cars from the 1960s & 1970s the press-on end that fits onto the tube is still there but the nylon sock part of the strainer is gone!

The gasoline over time ate it away!