Chrysler Airtemp Model 4216-51(??), S/N 2J646773

Anybody know where is the best place online to get a BOM or manual for above foced air heater. Understand Chrysler sold line to Fedders. Is that true? Came home last winter to find heater running open loop without ability to switch off via thermostat. Had to unplug AC to stop blower. Found wires leading to heater transformer inside unit somehow got burned and melted to other wiring probably causing short that let heater run open loop. Heater still good so I just want to rewire heater via electrician but I may need to replace transfornmer. I just want to replace wiring. Is this possible? Don’t need expense of replacing entire unit just yet as winter’s in Calif are relatively mild.

Any thoughts??