What was found
RETURNING FROM A FLIGHT, PILOT SHUT DOWN ENGINE, RADIO MASTER, THE A/C MASTER. WHEN MASTER WAS SHUT OFF, PILOT HEARD A POP FROM THE RIGHT SIDE OF PANEL. HE CHECKED BREAKERS, NOTICED NONE BLOWN, BUT SMELLED; NOTICE SMOKE COMING FROM BEHIND PANEL TO LEFT OF CIRCUIT BREAKERS. WHEN INVESTIGATED, FOUND RHEOSTAT ASSEMBLY WIRING AND COMPONENTS BURNT FOR CABIN LIGHT CONTROLS. PART WAS REPLACED WITH SERVICABLE ASSEMBLY.