AFTER CHANGING A NOSE LANDING GEAR STEERING HARNESS ON A DHC-8-400; A MECHANIC IS INFORMED OF A NOSE STEERING PROBLEM AND DAMAGED CANON PLUG.

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ON JUL/XA/08 I WAS ASSIGNED TO ACFT X. IN ZZZ MAINT HANGAR; ONE OF THE TASKS THAT NEEDED TO BE PERFORMED FOR THAT NIGHT ON THE ACFT WAS REMOVING AND REPLACING THE NOSE LNDG GEAR STEERING HARNESS. I CHOSE TO DO THAT TASK SINCE I HAVE NEVER DONE IT BEFORE. AFTER ORDERING THE PART AND GETTING THE REQUIRED TOOLS AND AMM; I STARTED THE TASK. WHILE REMOVING THE STEERING HARNESS; I REMOVED A BOLT ON THE BRACKET FOR THE NOSE LNDG GEAR STEERING HARNESS TO GAIN ACCESS TO A CLAMP TO REMOVE IT. AFTER REMOVING THE OLD STEERING HARNESS; I STARTED TO INSTALL THE NEW ONE IN ACCORDANCE WITH THE AMM. WHEN I GOT TO THE STEP TO INSTALL ONE OF THE CANNON PLUGS; I HAD A VERY DIFFICULT TIME GETTING IT ON. WHEN I GOT IT ON FINALLY IT DIDN'T LOOK RIGHT TO ME. I ASKED A FELLOW MECH WHAT HE THOUGHT; AND HE SAID THAT I WOULD HAVE TO REPOSITION THE CANNON PLUG. SO I RE-CLOCKED THE CANNON PLUG AND MOVED ON TO THE NEXT STEP. I FINISHED THE TASK AND PERFORMED THE OPS TEST. OPS TEST WAS GOOD; SO I SIGNED THE TASK OFF. THE NEXT DAY THAT I CAME TO WORK I WAS TOLD THAT THE SWING SHIFT MECHS WERE GETTING READY TO TAXI THE PLANE TO THE GATE AND THEY GOT A NOSEWHEEL STEERING CAUTION MESSAGE. MY LEAD TOLD ME THAT I HAD INSTALLED THE CANNON PLUG IN WRONG AND LEFT THE HARDWARE OFF OF THE BRACKET. HE TOLD ME THAT I WAS ON ACFT X TO FIX IT. AFTER INSTALLING A NEW NOSEWHEEL STEERING HARNESS ON JUL/XB/08 WE WERE PERFORMING THE OPS FUNCTION TEST AND THE NOSEWHEEL STEERING WOULD NOT COME ON AND WE WERE STILL GETTING THE CAUTION MESSAGE. AFTER FURTHER INVESTIGATION; WE FOUND THAT THE REASON WHY WE WERE GETTING THE CAUTION MESSAGE WAS DUE TO A BROKEN WIRE ON THE BACK OF THE NOSEWHEEL STEERING TILLER. I THINK THAT THE EVENT OCCURRED BECAUSE I WAS NOT PAYING ATTN TO DETAIL. AFTER BEING ASSIGNED TO ACFT X THE NEXT NIGHT; I COULD SEE WHERE THINGS WENT WRONG. IF I WOULD HAVE STUCK TO THE MANUAL INSTEAD OF ASKING ANOTHER MECH I WOULD HAVE NOT MADE THE MISTAKE. RIGHT AFTER THE STEP IN THE AMM THAT TELLS YOU TO INSTALL THE CANNON PLUG THERE IS A WARNING THAT TELLS YOU THAT YOU MIGHT HAVE TO REPOSITION THE CANNON PLUG AND TO MAKE SURE THAT IT IS FACING FORWARD/AFT. I COCKED IT SO THAT WHEN WE DID THE GEAR SWING THE ACTUATOR BRACKET SMASHED THE CANNON PLUG. I FORGOT TO TIGHTEN THE ATTACHING HARDWARE FOR THE BRACKET. I THINK THAT I WAS JUST NOT PAYING ATTN TO DETAIL. READ ALL STEPS PROVIDED IN THE AMM AND TASK CARDS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE DHC-8-400 NOSE WHEEL STEERING (NWS) TILLER IS ELECTRICALLY ACTIVATED BY A SWITCH JUST FORWARD OF THE STEERING TILLER ON THE CAPTAIN'S SIDE. THE ORIGINAL PROBLEM OF NWS CAUTION MESSAGE; NOTED BY THE SWING SHIFT TAXI CREW; WAS NOT ASSOCIATED WITH THE HARNESS HE HAD ORIGINALLY REPLACED. A BROKEN WIRE ON THE BACK SIDE OF THE TILLER WAS THE PROBLEM. BUT; REPORTER STATED THE DAMAGED CANON PLUG THAT WAS ALSO FOUND DAMAGED; WAS THE ONE HE HAD NOT POSITION CORRECTLY IN A FORWARD-AFT ORIENTATION THAT CONNECTED TO A GEAR POSITION SENSOR ON THE LEFT SIDE OF THE NLG; LOOKING FORWARD; NEAR THE RETRACT ACTUATOR. REPORTER STATED A NOSE GEAR SWING WAS REQUIRED AFTER HE REPLACED THE ORIGINAL NWS HARNESS. BUT; THEY COULD NOT USE HYDRAULICS DUE TO OTHER MECHANICS WORKING ON A HYDRAULIC LINE FOR ONE OF THE MAIN GEARS. INSTEAD; HE AND TWO OTHER MECHANICS JUST PUSHED THE NOSE GEAR UP INTO THE RETRACT POSITION UNTIL THEY HEARD THE UPLOCK ENGAGE. REPORTER STATED NONE OF THE MECHANICS WITH HIM; NOTED ANY DISCREPANCY; OR DAMAGED CANON PLUG AT THE SENSOR SUPPORT BRACKET.