DURING THE REMOVAL AND REPLACEMENT OF THE #4 AND #5 LEFT-HAND COCKPIT EYEBROW WINDOWS ON A B737-300; AN INSPECTOR INADVERTENTLY AGREED AND AUTHORIZED A MECHANIC TO TORQUE BOTH WINDOWS TO THE #4 WINDOW TORQUE VALUES.

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REMOVED AND REPLACED #4 L-HAND FLT DECK EYEBROW WINDOW AND #5 FLT DECK WINDOW L-HAND PER ENGINEERING AUTH. TORQUED #5 WINDOW SAME VALUE AS #4 WINDOW. 55-60 INCH LBS WHEN IT IS SUPPOSED TO HAVE BEEN 20-25 INCH LBS. INSPECTION HAD ADVISED ME AND AT THE NEXT ROUTINE OVERNIGHT DEST AND THE WINDOW WAS CHANGED. NO DEFECTS WERE NOTED WITH THE PREVIOUS WINDOW. READ MAINT MANUAL AND SAW #4 AND #5 TOGETHER FOR REMOVAL AND INSTALLATION. MISSED #5 WINDOW TORQUE VALUE AND TORQUED TO #4 WINDOW TORQUE VALUE; BEING TOGETHER FOR REMOVAL AND INSTALLATION. SUPPLEMENTAL INFO FROM ACN 812839: I HAD WORKED ON ACFT EXAMINING THE L-HAND #4 AND #5 COCKPIT WINDOWS. AFTER DETERMINING THE 2 WINDOWS WERE DELAMINATED; REMOVAL AND REPLACEMENT WAS IN PROGRESS. IN THE PROCESS; I INADVERTENTLY AGREED AND AUTHORIZED BOTH WINDOWS TO BE TORQUED TO THE SAME VALUES AT 55 INCH LBS AND COMPLIED WITH THE REMAINDER OF THE INSTALLATION WITH NO FURTHER INCIDENT. IN REALITY; L-HAND #5 WINDOW REQUIRES ONLY 20-25 INCH LBS (RESULTING IN AN OVER-TORQUE REALIZING LATER). AS I WAS WORKING DAYS ON ANOTHER ACFT THAT MORNING (6-7 HRS LATER); REPLACING L-HAND #4 COCKPIT WINDOW; WAS WHEN I DISCOVERED THAT A MISTAKE HAD BEEN MADE ON MY PREVIOUS ACFT. I IMMEDIATELY NOTIFIED MY SUPVR AND HE MADE ARRANGEMENTS TO HAVE THE WINDOW EVALUATED AND WAS PROMPTLY CHANGED AFTER LNDG. I SHOULD HAVE BEEN MORE DETAILED BUT SOMEHOW FAILED TO DETECT IT AT THE TIME; FURTHER JOBS AND WORK CARDS WILL BE MORE CAUTIOUSLY EXAMINED UNDER BETTER LIGHTING. MISREAD AMM AND PERHAPS LIGHTING COULD HAVE BEEN BETTER.