McDonnell Douglas Undifferentiated or Other Model
Maintenance Airframe; Maintenance Powerplant
Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft; Human Factors; Incorrect / Not Installed / Unavailable Part
During work on the Number 3 Engine Thrust Reverser (T/R); I closed the T/R Control and T/R Lock Control Circuit Breakers (C/B). They had been opened for the deferral of the Reverser. When I opened the Circuit Breakers; they had red collars that I left attached to make finding them easier. When I re deferred the Thrust Reverser System; I pulled the circuit beakers with the red collars and flipped the collars back around. They were in the correct area and I didn't think to look at the labels. Possibly someone knocked off the circuit breaker collar and put it back in the wrong place; compounded by my not verifying the circuit breakers I was pulling for the deferral. [Recommend] properly identifying the circuit breakers being pulled; instead of depending on a marker being in the correct position. Dayshift.
An Aircraft Maintenance Technician (AMT) reports he did not verify Circuit Breakers (C/B) he had opened and attached red collars to; were the correct C/Bs for a re-deferral of Number 3 Engine Thrust Reverser on a McDonald Douglas widebody aircraft.