Itinerant Air-Cooled

I bought a new sender for my '77 bay - the guy who's fitting it says when he tested it with an ohms meter, he did not get a variable response from it as he expected - just a constant signal all the way through. Does this mean it's broken?

Assuming he's using the meter correctly, then yes, that sender is defective. A good sender will read from about 10 ohms to about 70 ohms through its range.