Hey PatD,
I would do some investigation of the wiring connections and the possibility of a defect in the switch before concluding the transformer is bad. If it works at the lower settings, I would doubt a bad transformer and look at the connections, and do a continuity test on the switch positions. Be a lot easier to replace just a switch. Good Luck.....Denny

Denny has good advice, as always. If someone moved the range selector under load they could have burned away the contacts. These machines are pretty simple inside, but the owners manual doesn't offer much help for Your problem. You could check for voltage between the gun feed [cable conected to the outgoing side of the feeder] and the conections from the transformer to the range selector. This should show about 50 volts when the contactor is closed [when the gun trigger is pulled]. You need to be really carefull working on the machine with the covers open, there are plenty of electrically hot parts. If you have voltage at all 3 conections I would suspect the range selector switch. That high range isn't needed for dip transfer, but I guess You would need it for spray.