ACR MLG ACFT DEV FROM PRESCRIBED HOLDING PATTERN TURN TRACK DUE TO MISHANDLING CIRCUIT BREAKERS WHILE CORRECTING ANOTHER PROBLEM.

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PRIOR TO DEP; MAINT WAS WORKING TO REPAIR OVERHEAD PANEL RHEOSTAT. AFTER ENG START AND TAXI OUT; OVERHEAD PANEL RHEOSTAT WORKED NORMALLY; BUT AISLE STAND FLOOD LIGHT COULD NOT BE DIMMED OR SWITCHED OFF AND WAS FULL BRIGHT. ATTEMPTED TO LOCATE CIRCUIT BREAKER PRIOR TO TKOF; BUT COULDN'T; AND ELECTED TO TRY TO FIND IT IN CRUISE. FINALLY LOCATED; PULLED BREAKER DURING DSCNT ON THE BUCKO 3 ARR INTO DCA. DURING THIS TIME I WAS OUT OF MY SEAT AND CAPT WAS FLYING WITH HEADSET ON AND COCKPIT SPEAKERS OFF. UPON RETURNING TO MY SEAT ACFT WAS JUST LEVELING AT 15000 FT DECELERATING FROM 220 TO 210 HOLDING SPD ABOUT 2 MI FROM INTXN. THE AUTOTHROTTLES DID NOT ADVANCE AT ALL. CAPT APPLIED PWR AGGRESSIVELY AND WE REGAINED LOST SPD. ACFT HAD BEGUN ITS TURN INTO THE HOLD WHILE THIS SPD EVENT WAS OCCURRING. NOW ESTABLISHED ON THE OUTBOUND LEG AND CHKING THE STAR CHART; THE ACFT HAD MADE A R HOLDING PATTERN INSTEAD OF THE DEPICTED ONE TO THE L. WE TURNED THE ACFT R; BACK TO THE FIX TO CORRECT THE ERROR. ATC CALLED TO ASK IF WE HAD MADE A R TURN. THE CAPT GAVE A BRIEF EXPLANATION. THE CAPT'S CDU WAS STILL ON THE HOLD PAGE FROM WHEN HE'D INITIALLY PROGRAMMED THE HOLD AND ALL ENTERED DATA WAS CORRECT INCLUDING L FOR TURN DIRECTION OF HOLD YET NAV CRT'S SHOWED R TURN HOLDING PATTERNS. CAPT REENTERED HOLD 3 MORE TIMES WITH L TURNS AND 3 TIMES THE CRT DEPICTED R TURN PATTERNS. ONLY ON THE FOURTH ATTEMPT DID THE L TURN PATTERN APPEAR. A SIMPLE MALFUNCTIONING FLOODLIGHT WITH A DIFFICULT TO FIND CIRCUIT BREAKER STARTED THIS EASILY PREVENTABLE MISTAKE. HAD WE TAKEN A FEW MORE MINS PRIOR TO TKOF TO LOCATE AND PULL THE CIRCUIT BREAKERS; THERE WOULD HAVE BEEN 2 PLTS MONITORING THE FLT TO CATCH THE ERROR OF CONTRADICTION BTWN FMC AND CRT AND THE AUTOTHROTTLE'S LACK OF RESPONSE.