An access control door that won’t unlock is more than an inconvenience. On an egress door, it can be a life safety violation — if people can’t get out, the system is failing its primary function. On a security door, it means the building isn’t secured the way it should be.
Most access control failures fall into five categories. Knowing which one you’re dealing with speeds up the repair and tells you whether it’s a quick fix or a service call.
1. Power Supply Failure
The most common reason a door won’t unlock is that the lock isn’t getting power. Every electric strike, magnetic lock, and electric trim device requires a power supply — typically 12V or 24V DC. If the power supply fails, the behavior depends on the lock type:
- Fail-secure locks (electric strikes, most electric trim): stay locked. The door won’t unlock electronically. The mechanical key override still works.
- Fail-safe locks (magnetic locks): unlock. The door stays unlocked until power is restored. This is the correct behavior for egress doors.
Power supply failures come from a blown fuse or tripped breaker on the power supply, a failed battery backup (the battery was carrying the load after a power outage and has drained), a disconnected or cut wire between the power supply and the lock, or a power supply that’s under-sized for the number of locks on the circuit.
Quick check: Look at the power supply. Is the power LED on? If the supply has a voltage meter, is it reading 12V or 24V? If the supply is dead, check the circuit breaker or fuse first.
2. Wiring Failure
The wire between the controller and the lock carries the unlock signal. The wire between the power supply and the lock carries the power. Both are low-voltage, and both run through the door frame — a path that’s vulnerable to chafing, water intrusion, and physical damage.
On aluminum storefront doors, the wiring typically routes through the frame extrusion, across the threshold, and to a controller box mounted nearby. The transition points — where the wire exits the frame and enters the floor, and where it enters the controller — are where failures happen.
Signs of a wiring failure: the controller sends the unlock signal (the relay clicks) but the lock doesn’t release, the lock works intermittently, the lock buzzes or clicks but doesn’t fully release, or other doors on the same controller work fine.
Quick check: If the controller relay clicks but the lock doesn’t release, the problem is between the controller and the lock — either the wiring or the lock itself. A multimeter at the lock end will tell you whether voltage is arriving.
3. Mechanical Misalignment
The access control system can be working perfectly — power is present, the controller sends the signal, the lock releases — but the door still won’t open because the mechanical hardware is out of alignment.
This happens when the door has sagged on worn hinges and the latch bolt no longer aligns with the strike opening, the frame has settled and shifted the strike position relative to the latch, or the electric strike releases but the latch bolt is binding against the lip of the strike instead of passing through.
On a magnetic lock, mechanical misalignment means the armature plate (on the door) doesn’t fully contact the magnet (on the frame). The magnetic holding force drops, and the door may not stay locked — or may be hard to open because the armature is dragging.
Signs of mechanical misalignment: the lock releases (you hear the click or buzz) but the door won’t push open, the door opens but is hard to push, the lock works in some seasons but not others (thermal expansion shifts the frame), or there are wear marks on the latch bolt or strike lip.
Quick check: When the lock releases, try lifting the door slightly while pushing. If it opens more easily when lifted, the hinges are worn and the door has sagged.
4. Controller or Software Failure
The access controller is the brain of the system. It receives the credential from the reader, checks it against the authorized list, and sends the unlock signal to the lock. If the controller fails, the door doesn’t unlock — even if the power supply and wiring are fine.
Controller failures come from a network outage (if the controller is networked and the credential database is hosted on a server, the controller can’t verify the credential), a firmware crash (a reboot usually fixes it), a full credential database, or a corrupted credential (the card or fob’s data has degraded or been damaged).
Signs of a controller failure: the reader doesn’t respond when a credential is presented (no beep, no LED change), some credentials work and others don’t, the controller’s status LED is off or showing an error pattern, or all doors on the same controller are affected.
Quick check: Reboot the controller. Most networked controllers have a recessed reset button or a power-cycle procedure. If the door starts working after a reboot, the issue is firmware or network — not hardware.
5. Sensor Failure
On a door with a REX sensor (request-to-exit) or a DPS (door position switch), a sensor failure can prevent the system from unlocking. The controller may refuse to unlock the door because it thinks someone is already at the door (REX sensor stuck in the “person present” state) or because it can’t verify the door is closed (DPS failure).
This is less common than power or wiring failures, but it happens — especially on doors where the sensor has been knocked out of alignment, the PIR lens is dirty, or water has gotten into the sensor housing.
Signs of a sensor failure: the system logs show “door forced” or “door propped” alarms that don’t match reality, the lock won’t unlock even though the credential is valid, or the lock unlocks but immediately re-locks before the door can be opened.
Quick check: Check the sensor status in the controller’s software (if accessible). A stuck REX or DPS will show as “active” even when no one is at the door.
When to Call for Service
If the quick checks don’t identify the problem, or if the problem is in the wiring or the controller, it’s time for a service call. The most common service calls we handle:
- Wire replacement through door frames (the most common physical failure)
- Power supply replacement (fuses, batteries, or the supply itself)
- Strike or lock replacement (the internal solenoid has failed)
- Controller diagnostics and firmware updates
- Door realignment to fix mechanical interference
What Pro Locksmith Does
Pro Locksmith LLC troubleshoots, repairs, and services access control systems for commercial properties throughout Broward County and Miami-Dade, including Fort Lauderdale, Hollywood, Pembroke Pines, Davie, Pompano Beach, Coral Springs, and Miami. We diagnose power, wiring, mechanical, controller, and sensor issues — and we carry replacement hardware on the truck for common lock types. Licensed and insured. Flat-rate pricing quoted up front. COI provided. Employees, not subcontractors.
If your access control door won’t unlock, call Pro Locksmith LLC at (954) 406-8266.
Sources
- ANSI/BHMA A156.31, Electric Strikes
- NFPA 101, Life Safety Code (egress requirements for access-controlled doors)
- ADA Standards for Accessible Design, Section 404
- International Building Code, Chapter 10 (Means of Egress)