A B737-700 RETURNED TO GATE DUE TO ANTI-ICE VALVE DISCREPANCY. MECHANIC PERFORMING MEL PROCEDURE MISTAKENLY DISCONNECTED AND STOWED THE ANTI-ICE VALVE CANON PLUG INSTEAD OF THE REQUIRED TAI PRESSURE SWITCH CANON PLUG.

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THIS STARTED WITH A GATE RETURN FOR #1 ENG COWL ANTI-ICE VALVE DISCREPANCY. MR X AND I FOUND OUT THAT MEL WAS THE ONLY OPTION; BECAUSE WE HAD NO VALVE IN STOCK. RAIN WAS COMING DOWN AND WE WANTED TO GET THE PAX ON THEIR WAY SAFELY IN A TIMELY MANNER. WE READ THE MEL AND PROCEEDED TO WORK MAINT PROCS. HAD 2 PARTS. I TOOK THE FIRST; THAT WAS TO LOCK OUT THE COWL VALVE. MR X TOOK THE SECOND; WHICH WAS TO LOCK THE HIGH STAGE VALVE. MR X HAD NOTIFIED ME THAT THE BOLT TO LOCK THE HIGH STAGE VALVE HAD SHEARED; WHICH IS NOT UNCOMMON. MY FOCUS DIVERTED; BECAUSE I KNEW HIGH STAGE VALVE REPLACEMENT WAS NOT EASY. PER MAINT PROCS I HAD TO STOW THE TAI PRESSURE SWITCH CANON PLUG. IN ERROR I STOWED THE ANTI-ICE VALVE CANON PLUG. BOTH PLUGS ARE IN THE SAME AREA. I FEEL THE MEL PAPERWORK FOR THIS MAINT PROC IS TOO GENERIC; BUT I TAKE FULL RESPONSIBILITY FOR MY ERROR. IN THE FUTURE I WILL TAKE A STEP BACK AND CAREFULLY UNDERSTAND MY PAPERWORK SO THE ACFT WILL GO OUT SAFELY AND PROPERLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT PART OF THE MEL PROCEDURE MECHANICS USE; INCLUDES A DIAGRAM TO DISCONNECT THE TAI PRESSURE SWITCH CANON PLUG ON THE NOSE COWL ANTI-ICE VALVE; WRAP IT IN A PLASTIC BAG AND STOW THE CONNECTOR. HOWEVER; THERE ARE TWO CANON PLUGS ON THIS SAME ANTI-ICE VALVE IN CLOSE PROXIMITY TO EACH OTHER. THE MEL PROCEDURE DIAGRAM ONLY SHOWS ONE CANON PLUG WRAPPED AND STOWED ON THIS VALVE; WITHOUT ANY REFERENCE TO THERE BEING TWO DIFFERENT CONNECTORS. REPORTER ALSO STATED HE HAS DONE THIS PROCEDURE BEFORE. YET SOMEHOW; HE DIDN'T CATCH THE WORDING THAT REFERENCED THE PRESSURE SWITCH (TAI) ON THE DIAGRAM. INSTEAD; HE DISCONNECTED THE SHUT-OFF VALVE'S CONNECTOR. REPORTER STATED HE HAS REQUESTED TO HIS CARRIER THAT A REVISION BE MADE TO THE MEL DEFERRAL PROCEDURE TO INCLUDE BOTH CANON PLUG CONNECTORS. THE MM DIAGRAM DOES SPECIFICALLY SHOW THE DIFFERENT CANON PLUG CONNECTORS.