CPL Troubleshooting & Repair of Locks 3 — Questions and Answers
Question 1: A padlock shackle will not release after the correct key is fully turned. Which condition best explains this symptom?
- Incorrect key code
- Shackle under lateral load or tension (Correct answer)
- Worn plug warding
- Incorrect keyway
Correct answer: Shackle under lateral load or tension
Padlock shackles under lateral tension or load bind the locking dog and prevent release even after the plug rotates correctly; tension must be relieved before the shackle will open.
Question 2: Which symptom most clearly indicates that a lock's plug has excessive side play (slop) within the shell?
- Key inserts too easily
- Lock can be picked with minimal tension
- Plug wobbles during key insertion with no binding on pins (Correct answer)
- Driver pins protrude below the shear line
Correct answer: Plug wobbles during key insertion with no binding on pins
Excessive side play causes the plug to wobble without properly engaging the pins, indicating wear between the plug and shell.
Question 3: A technician is troubleshooting a Schlage B-series deadbolt where the inside thumbturn works but the key cylinder does not retract the bolt. The most likely fault is:
- Stripped cam on the cylinder (Correct answer)
- Broken thumbturn spindle
- Misaligned strike plate
- Defective door closer
Correct answer: Stripped cam on the cylinder
If the thumbturn operates correctly but the key side does not, the cylinder's cam that drives the bolt mechanism is the component to suspect.
Question 4: After re-assembling a cylinder, the plug does not rotate freely with the correct key but did before disassembly. The technician should first check:
- Whether driver pins were accidentally swapped between chambers (Correct answer)
- If the keyway is the wrong profile
- Whether the strike is misaligned
- If the door gap is too wide
Correct answer: Whether driver pins were accidentally swapped between chambers
Swapping driver pins of different lengths between chambers during disassembly can cause false shear lines or binding, preventing smooth rotation.
Question 5: A lever handle lock returns to the horizontal position slowly or not at all after being depressed. The technician should inspect the:
- Cylinder cam
- Return spring or spring cage (Correct answer)
- Latch bolt face
- Deadlocking plunger
Correct answer: Return spring or spring cage
The lever return spring or spring cage is responsible for returning the lever to its resting position; failure of this component causes the slow or no-return symptom.
Question 6: When inspecting a high-security lock cylinder for wear, which measurement tool is used to verify pin chamber depth tolerance?
- Feeler gauge
- Plug follower
- Depth gauge or micrometer (Correct answer)
- Key gauge
Correct answer: Depth gauge or micrometer
A depth gauge or micrometer measures pin chamber tolerances precisely to identify wear beyond manufacturer specifications in high-security cylinders.
Question 7: A customer complains that their electronic keypad lock's motor runs but the bolt does not move. The mechanical fault is most likely in the:
- Keypad membrane
- Coupling clutch or drive gear between the motor and bolt (Correct answer)
- Battery voltage level
- Programming module
Correct answer: Coupling clutch or drive gear between the motor and bolt
If the motor runs but the bolt is stationary, the mechanical coupling or drive gear between the motor output and the bolt mechanism has failed or slipped.
CPL Troubleshooting & Repair of Locks 3
A padlock shackle will not release after the correct key is fully turned.
Which condition best explains this symptom?