47 Chrysler gas gauge

[47windsor]

Good afternoon, I just put over 800 miles on the car & the gas gauge worked perfectly, after leaving the car for 2 to 3 weeks the gas gauge reads empty. I know I arrived home with approx 3/4 of tank. Without jumping to conclusions that it must be the the gauge or it must be the tank float unit, how can I test to find out what the problem is.  I don't have a spare tank to use as suggested in the manual, any help would be appreciated.

Regards

 

Bruce Watson