What was found
ON INITIAL T/O AT 50KTS THE NR 1 REV LIGHT ILLUMINATED, WE REJECTED THE TAKEOFF. AS SOON AS POWER WAS REDUCED THE LIGHT WENT OUT. TAXI'D BACK TO RWY FOR T/O AND AT POWER UP THE NR 1 THRUST REV LIGHT ILLUMINATED AGAIN AND T/O WAS REJECTED. THIS IS A REPEAT WRITE-UP. WAS ABLE TO DUPLICATE FAULT ON GROUND. FOUND RIGHT STOW SWITCH KEY WASHER STRIPPED ALLOWING SWITCH TO ROTATE, SHAKING SWITCH CAUSED REVERSE LIGHT TO ILLUMINATE. NEW SWITCH ARRIVED HRL WITHOUT WASHER AND NUTS.NEED KEYED WASHER.DEACTIVATED THRUST REVERSER PER MEL 78-30-01-C.ITEM REMAINS DEFFERED. REMOVED AND REPLACED RIGHT HAND T/R DEPLOY SWITCH PER M.M. 78-31-18-4, RIG AND OPS CHECK NORMAL. A/C OK FOR SERVICE.