Narrative:

After approximately 2 hours at cruise; happened to notice that the window heat switches were not in the 'on' position. We had kept the aircraft on a turn to anc and; therefore; were following through-flight procedures on preparation and checklist items. After thinking about how they came to be off (they were on when we landed; without question); we decided that we had the answer. We had written up the windshields for a cleaning due to multiple insect strikes. The suspicion is that the maintenance technician turned the window heat off to clean the windows; and then forgot to turn them back on again. I do not know if there is a task card for cleaning or not; and I am sure it was an oversight. The technician seemed alert; responsive and serious about his work; and signed the log off for us; and he did a great job on the windows. The problem is that window heat is not on the through-flight checklist; and it has no backup such as illuminating on recall to let you know they are off. The checklist itself is the only backstop. Ironically; we had commented on the new checklist changes; particularly the pressurization mode selector to automatic. Since it is not on the through-flight either; we commented that there could be a miss there if you situation on the ground for a relatively long period of time in cold WX. Maintenance has been known to manually close the outflow valve; and some crews do as well; it would easily be overlooked in the through-flight situation. All items that do not have some form of backup; either recall or other means of notifying the crew of status; must be included on the through-flight checklist. Just because you brought the airplane in and are taking it out; does not mean that someone hasn't changed confign such as in our case.

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Original NASA ASRS Text

Title: A B737-900 FLT CREW IN CRUISE FLT NOTICED THE WINDSHIELD HEAT SWITCHES HAD BEEN TURNED OFF BY MAINT AND HAD NOT BEEN TURNED ON.

Narrative: AFTER APPROX 2 HRS AT CRUISE; HAPPENED TO NOTICE THAT THE WINDOW HEAT SWITCHES WERE NOT IN THE 'ON' POS. WE HAD KEPT THE ACFT ON A TURN TO ANC AND; THEREFORE; WERE FOLLOWING THROUGH-FLT PROCS ON PREPARATION AND CHKLIST ITEMS. AFTER THINKING ABOUT HOW THEY CAME TO BE OFF (THEY WERE ON WHEN WE LANDED; WITHOUT QUESTION); WE DECIDED THAT WE HAD THE ANSWER. WE HAD WRITTEN UP THE WINDSHIELDS FOR A CLEANING DUE TO MULTIPLE INSECT STRIKES. THE SUSPICION IS THAT THE MAINT TECHNICIAN TURNED THE WINDOW HEAT OFF TO CLEAN THE WINDOWS; AND THEN FORGOT TO TURN THEM BACK ON AGAIN. I DO NOT KNOW IF THERE IS A TASK CARD FOR CLEANING OR NOT; AND I AM SURE IT WAS AN OVERSIGHT. THE TECHNICIAN SEEMED ALERT; RESPONSIVE AND SERIOUS ABOUT HIS WORK; AND SIGNED THE LOG OFF FOR US; AND HE DID A GREAT JOB ON THE WINDOWS. THE PROB IS THAT WINDOW HEAT IS NOT ON THE THROUGH-FLT CHKLIST; AND IT HAS NO BACKUP SUCH AS ILLUMINATING ON RECALL TO LET YOU KNOW THEY ARE OFF. THE CHKLIST ITSELF IS THE ONLY BACKSTOP. IRONICALLY; WE HAD COMMENTED ON THE NEW CHKLIST CHANGES; PARTICULARLY THE PRESSURIZATION MODE SELECTOR TO AUTO. SINCE IT IS NOT ON THE THROUGH-FLT EITHER; WE COMMENTED THAT THERE COULD BE A MISS THERE IF YOU SIT ON THE GND FOR A RELATIVELY LONG PERIOD OF TIME IN COLD WX. MAINT HAS BEEN KNOWN TO MANUALLY CLOSE THE OUTFLOW VALVE; AND SOME CREWS DO AS WELL; IT WOULD EASILY BE OVERLOOKED IN THE THROUGH-FLT SIT. ALL ITEMS THAT DO NOT HAVE SOME FORM OF BACKUP; EITHER RECALL OR OTHER MEANS OF NOTIFYING THE CREW OF STATUS; MUST BE INCLUDED ON THE THROUGH-FLT CHKLIST. JUST BECAUSE YOU BROUGHT THE AIRPLANE IN AND ARE TAKING IT OUT; DOES NOT MEAN THAT SOMEONE HASN'T CHANGED CONFIGN SUCH AS IN OUR CASE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.