Frozen up heat riser valves are a common problem, and they're usually pretty simple to fix. Heat from a Propane or Acetyline torch ,penetrating oil, tapping the shaft side to side with a hammer, and lots of patience will usually free up the shaft. Soak, heat, tap, repeat- - - - - - -over and over. Once it breaks free be sure the flap can move through its full travel, install a new thermal spring, and press on. The thermal spring on Ebay advertised for a Jeep is less than half price of the outrageously expensive OEM style ones the resto-ripoff places sell.
Jerry
