New sending unit reading full

I replaced the sending unit in my 1968 Bronco, and it reads full with only 5 gallons in the tank. Is the new unit bad?

Welcome Michael..,

What was the old sender doing that precipitated the change out..?

Additional info. would help but a guess would be a short in the wire leading to the gage.

Pull the wire off the sender .., the gage should drop to "O"

Did the new sending unit go into place freely with no hangups.., with the float in the down position..?

The "new" units are ohms tested prior to packing & shipment however, they're a bit fragile.

I put a new one in my stock rear tank and it reads empty with about 4 gals left....  You think I got a front tank sending unit?

I had a spare aux. tank here but the wind knocked it off the shelf & cracked it.  I removed/saved all the hardware, including the sender.  I could not see any obvious difference between the two senders.

Having said that, I'm not sure how accurate these fuel level indicator systems are/were from the factory..., or any other indicator systems from that time period for that matter.

What I did with mine was attach the sender wires while out of the tank.., then moved the float up & down while watching the dash gage.  If it indicated full, at or near the top of stroke, & empty at or near the bottom.., I was happy.

On some.., I bent the float arm slightly to adjust but again.., I think these are "best-guess" indicators..., not life savers.

If the oil & temp gages are reading correctly (or nearly so), then the mini voltage regulator on the back of the instmt. cluster is good.

It powers all three gages. (+ - 6V)

The dash gages are factory adjusted/set. They are re-adjustable but, very delicate..., not advisable.

I just patched my aux tank and getting ready to re-install it.  I am going to run to Tom's w/ a tester to see if there in a difference....  May buy a new "main" one and do a swap or pull it a make a mechanical adjustment (bend the arm).  It's kind of nice knowing you have a couple of gallons in "reserve" though....