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)
Reader Problems: When the Credential Never Reaches the Controller
The five categories above assume the reader did its job. Sometimes it did not. A card reader is a small radio and a small computer, and it can fail on its own while the controller, power supply and lock are all healthy. The clue is usually the reader’s own lights and sounds. If a card is presented and the reader shows no change at all, the reader may have lost power, lost its data connection, or never been able to read that type of card in the first place.
Card format mismatches are more common than people expect. Older proximity cards operate at a low frequency, while newer smart cards and many phone credentials operate at a higher one. A reader built for one will simply ignore the other. This shows up after a company orders replacement cards from a different supplier, or after a new tenant brings badges from a previous building and assumes they will work. The cards are fine and the reader is fine. They just do not speak the same language.
The wiring between reader and controller matters as well. Many older systems use a one-way protocol that sends the card number to the controller and nothing else. Newer installations often use a two-way supervised protocol that lets the controller notice when a reader has been disconnected or tampered with. Mixing the two, or losing one conductor in an older one-way run, can produce a reader that beeps and flashes normally but sends a garbled number that the controller rejects every time.
- Reader dark with no lights: check reader power first, then the cable at the controller end.
- Reader flashes but every card is denied: suspect a data wiring fault or a card format mismatch.
- One person’s card fails while everyone else gets in: the problem is almost always that card or that person’s record in the software.
Schedules, Holidays and Clocks
A surprising number of “broken” doors are working exactly as programmed. Access systems run on schedules. A door can be set to stay unlocked during business hours, lock at close, and only admit certain groups after hours. If someone set a holiday schedule and forgot to remove it, the door may treat an ordinary Tuesday as a closed day and refuse credentials that worked yesterday.
Clock drift causes a quieter version of the same problem. A controller that lost its time setting during a power outage may believe it is the middle of the night. Staff whose access is limited to business hours will be denied, while managers with round-the-clock access get in normally, which makes the fault look random. Daylight saving changes can do the same thing on systems that do not update automatically. When a door starts misbehaving right after a power event or a time change, the controller’s clock is worth checking before anyone touches hardware.
Some systems also use a first-person-in rule, where the door stays locked until an authorized supervisor badges in, and only then switches to its unlocked schedule. If that supervisor is out sick, the door never unlocks for the day. That is a policy setting, not a failure, but it produces exactly the same phone call.
Anti-Passback and Lockdown Settings
Anti-passback is a feature that stops one card from being used to let two people in. If the system believes a cardholder is already inside, because they entered without badging out, it may refuse that card at the entry reader. This is common in parking structures and secure suites. People experience it as “my card stopped working,” when in reality the system is enforcing a rule. An administrator can reset the cardholder’s status from the software.
Lockdown functions work similarly. Some systems allow a manager to trigger a building-wide lockdown from a button or an app. If a lockdown was triggered during a drill or by accident and never cleared, doors will ignore normal credentials until someone with the right permission releases it.
Electric Strike Preload and Door Pressure
An electric strike releases the latch by letting its keeper swing out of the way. If the latch is pressed hard against that keeper, the strike may not be able to release it. This is called preload. It happens when a door is pulled tight by heavy weatherstripping, when air pressure inside the building pushes the door against the frame, or when someone is pulling on the handle before the strike fires. The strike buzzes, nothing moves, and the person tries again with the same result.
In South Florida, air conditioning systems that pull a building slightly negative or positive can make this worse on exterior doors, especially tall storefront doors with a lot of surface area. A strike rated for higher preload, an adjustment to the keeper, or balancing the building’s air pressure can all solve it. The simplest test is to present the credential without touching the door, then push only after the strike releases. If the door opens that way every time, preload is the likely cause.
Electrified Exit Devices and Latch Retraction
Doors fitted with electrified exit devices behave differently from strike doors. Some use electric trim, where the outside lever becomes active when power is applied. Others use motorized or solenoid latch retraction, where the bar’s latch is physically pulled in so the door can be pushed open from outside. These mechanisms draw more current at the moment of release than a strike does. A power supply that is fine for strikes can sag under that inrush, and the device may click without fully retracting.
Latch retraction devices also depend on correct adjustment inside the bar. After heavy use, the linkage can drift so that the motor completes its cycle but the latch stops short of fully clearing the strike. The door then drags or catches. A technician will check the device’s own diagnostic lights if it has them, confirm the supply is delivering the rated current, and adjust the retraction stroke.
Voltage Drop, Wire Gauge and Suppression
Low voltage wiring has limits that are easy to ignore during installation and hard to diagnose later. Long runs of thin wire lose voltage along the way. A supply may read correctly at its terminals while the lock at the far end of the building receives much less, just enough to work on a cool morning and not enough on a hot afternoon when resistance rises. Measuring voltage at the lock while it is being energized, not just at the supply, reveals this quickly.
Another hidden fault is missing surge suppression. When a coil in a strike or maglock turns off, it can send a voltage spike back down the wire. Most lock hardware and controllers expect a suppression diode or similar device at the lock to absorb it. Without one, the controller’s relay contacts slowly burn and eventually stop closing reliably. The symptom is a relay that clicks but a lock that only sometimes receives power. Replacing the relay without adding suppression means the problem returns.
Polarity and current type also matter. Some strikes are built for direct current only, and wiring them backward or feeding them alternating current will cause buzzing, heat, or failure. When a strike has been replaced recently and the trouble started right after, the replacement’s rating is one of the first things to confirm.
Fire Alarm Interface Problems
In many buildings, the fire alarm system is connected to access controlled doors so that locks release when an alarm occurs. That connection usually runs through a relay that cuts power to fail-safe locks. If the fire alarm panel is in trouble, has been placed in a test mode, or if its relay has failed, doors may behave strangely. A maglock that should hold may stay released, or a door that should unlock on alarm may not. Any problem on this interface needs to be handled with the fire alarm contractor involved, because changes can affect the building’s life safety system and its inspection records.
What to Write Down Before You Call
Good notes shorten a service call. Before calling for help, collect as much of the following as you can:
- Which door or doors are affected, and whether other doors on the same system are working.
- Whether the reader shows any response to a credential, and what it looks and sounds like.
- Whether you hear the lock click, buzz, or do nothing when a valid credential is presented.
- When the problem started, and whether anything happened around that time, such as a storm, power outage, construction, or software change.
- Whether the mechanical key override still opens the door.
- The brand of the system and who manages the software, if you know.
This information lets a technician bring the right parts and start in the right place instead of testing every component from scratch.
Keeping the Building Safe While the Door Is Down
While a door is out of service, two priorities compete: people must be able to get out, and the building should not be left open. Never block, chain, or padlock an egress door to compensate for a failed access control lock. If a fail-safe lock has released and the door is unsecured, it is better to post a staff member, adjust staffing, or use the mechanical lock if the door has one and code permits, than to add hardware that could trap people during an emergency. If you are not sure what is allowed on a particular opening, ask before improvising.
Preventive Checks That Stop Most Failures
Many of the failures described on this page can be caught early with a simple routine. Test the battery backup on each power supply by briefly cutting main power and confirming the locks still operate. Replace backup batteries on the schedule the manufacturer recommends, since sealed batteries lose capacity with age even if they have never been used. Walk each controlled door, present a credential, and watch the lock release and the door open without effort. Look for chafed cable at door hinges and transfer points. Review the system’s event log for repeated forced door or held open alarms, which often point to a mechanical issue before it becomes a lockout.
Pro Locksmith services access control openings across Broward County and north through Boca Raton and Delray Beach, with commercial work extending to West Palm Beach, and south through Aventura, North Miami, Coral Gables and Coconut Grove. When a controlled door stops unlocking and the quick checks do not solve it, call (954) 406-8266 and describe what you are seeing.