Maintenance Airframe; Maintenance Powerplant
Troubleshooting; Time Pressure; Communication Breakdown; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action; General Flight Cancelled / Delayed
Company Policy; Manuals; Procedure
Aircraft X was in for maintenance and it had two MELs that were not scheduled to be worked on due to part shortages. They were both related to one problem with the APU cross flow auto function. When the aircraft was taxing out for departure the next morning; the left engine standby fuel pump failed and the aircraft returned to the gate. This could not be MELed because of APU pump MEL. We brought plane back to hanger and no parts were in stock to fix current write up so decisions were made to rob parts from Aircraft Y. We decided to go for clearing APU related cross flow MEL and MEL the left standby fuel boost pump. I had printed the procedures and also started the paperwork process for the rob transaction. During this time; we missed noticing the pressure switch needing to be transferred and staying with the aircraft. The pump was inspected and a new tag was issued to install on the aircraft. I never looked at the pump and assumed the pressure switch was installed on the pump canister rather than the cartridge.The replacement pump/cartridge was installed and I took over for the operations and leak checks and looked over the installation not noticing the pressure switch issue where it had been transferred with the pumps. The log book entries were all documented by myself and the aircraft was returned to service. After I was at home; a day shift mechanic called saying that when he was draining the residual fuel from the part that was removed he noticed the pressure switch was still installed on removed part. After investigating he noticed the switches should have been swapped over to stay with the aircraft. He had contacted Maintenance Control and the proper documentation was completed to return the aircraft back to service. We as a company are constantly dealing with robbing parts from aircraft due to parts shortages and having to deal with this during hectic line operations. When we do have the parts they are not divided between bases equally causing many parts shortages.
Lead Technician reported that during a part swap; the proper procedure was not followed resulting in the incorrect installation of a pressure switch.