I just published an article in the POCA news on cleaning up and modernizing an early fuel gauge sender. The most often failed part is the curved strip inside the actual plastic sender, that has many turns of very fine wire wrapped around it. A contacter attached to the float arm slides over the windings to change the resistence and thus the gauge reading. In some cars, the contacter wears thru the windings. The fine wire is 0.012" dia- less than a hair so broken wires are not easy to spot. The plastic sender ass'y has a small removeable door in the side for inspection. The internal winding-piece is not separately replaceable nor repairable, but all the vendors have the more desirable late sender (with an integral fuel feed) in stock, and all senders perfectly retrofit all models. You'll likely have to remove yours to actually check it, and that's easy once the left rear quarter window is removed; the sender with its long float-arm simply pulls out thru the window opening. If you put a VOM across the gauge terminal & ground and swing the float arm, the resistence reading on the meter will change. If it doesn't, the fine wire winding is likely broken somewhere. Note there are 2 terminals; one is the gauge while the other is the low-fuel warning light in the dash. Wire colors vary according to year of your Pantera, too.
