Troubleshooting & Repair of Locks Flashcards

A commercial door closer with a lock requires repeated attempts to fully latch after each use. After confirming the lock and latch are functional, the technician should adjust the:

Answer: Door closer's latch speed (sweep speed) valve

The latch speed (sweep) valve on the door closer controls how fast the door moves through the final inches; too slow prevents the latch from engaging the strike reliably.

A padlock's combination dial spins but the shackle does not release at the correct combination. The most likely internal fault is:

Answer: A misaligned or worn drive cam or disc gate

A worn or misaligned drive cam or disc gate prevents the gates from aligning at the correct combination, so the locking bolt cannot retract to release the shackle.

When a high-security lock cylinder uses a secondary locking element (sidebar), a symptom of sidebar damage or wear is:

Answer: Lock opens with incorrect key bitting that passes the primary pins

A damaged sidebar may fail to block rotation even when the secondary tumblers are not properly aligned, allowing an incorrect key to operate the lock.

A lock technician notices that after installing a new cylinder, the key binds slightly on the down-stroke (turning clockwise) but not counter-clockwise. This typically indicates:

Answer: The plug is installed 180 degrees out of orientation

A plug installed with reversed orientation causes the cam to drive in the opposite direction of design, producing binding in one rotation direction only.

A technician is troubleshooting a failed key-in-lever lockset where the lever turns freely in both directions without retracting the latch. The component that has most likely failed is:

Answer: The clutch or spindle coupler inside the lever hub

Free rotation of the lever without latch retraction indicates the clutch or spindle coupler that transmits torque from the lever to the latch mechanism has stripped or disengaged.

A fire-rated door's latch does not retract when the panic bar is depressed. Which step should the technician perform first?

Answer: Inspect the cross-bar linkage rods for bends, disconnection, or obstructions

The cross-bar linkage rods transmit force from the panic bar to the latch; bends, disconnections, or obstructions in these rods are the most common cause of latch failure in panic hardware.

When replacing springs in a pin tumbler cylinder, using springs that are too strong (high tension) will most likely cause:

Answer: Increased key insertion force and premature wear on the key cuts

Overly stiff springs press driver pins down with excessive force, requiring greater insertion effort and accelerating wear on both the key bitting and pin chambers.