Follow up, got a new heater rod, reamed the rust out of the extra tube as
impossible to get the old heater out with out damage. Works great. While I had the fridg out, discovered the area around the gas burner all rusted out, redid this are with galvanized sheet metal. Once the wind dies down here will check that out..was not cooling well on gas, figure I was loosing most of the heat.
Jim in Pima Az, enjoying our 1975 31 ft Airstream Sovereign