Access Control Troubleshooting: Fob or Card Not Working
Sorting a dead credential from a reader problem before calling out an engineer
Fob or card not working in Kent or Medway? We can help identify the cause.
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Access control troubleshooting starts with one question: is it one fob or everyone? If only one fob fails, it has usually been damaged, wiped or removed from the system. If every fob fails at one door, look at that reader, its power or the lock. If every door fails, the controller or its network connection is the likely cause.
Fobs and proximity cards are one of the most reliable parts of an access control installation, which is exactly why it is noticeable when one suddenly stops working. Most credentials are entirely passive, drawing power from the reader itself rather than holding their own battery, so a fob that fails to trigger the reader has usually been damaged, demagnetised, deleted from the system, or is being presented to a reader that has itself developed a fault.
The pattern of the failure tells you a lot. A single fob failing while everyone else's works fine points towards that one credential or its record in the system. Several fobs failing together, or an entire reader ignoring everything presented to it, points towards the reader, its cabling, or the controller behind it.
Working through a short set of checks before assuming the worst saves a wasted call out, and helps an engineer diagnose the actual cause faster when one is needed.
What You Will Usually Notice
Safe Checks You Can Do Yourself
Try a second known-working fob at the same reader
If a colleague's fob or a spare works fine at that door, the individual credential is the likely fault rather than the reader or the wider system, which narrows things down considerably.
Check the fob for physical damage
Look for cracks, deep scratches over the chip area, or signs it has been through a wash cycle. Physical damage to the embedded antenna inside a fob or card is a common and permanent cause of failure.
Test the same fob at a different reader
If your site has more than one access-controlled door, present the fob there too. A fob that works elsewhere but not at one specific reader suggests the reader itself, not the credential, needs attention.
Rule out keys or metal interference
Presenting a fob while it is still on a bunch of keys, or pressed against a phone or another card, can occasionally interfere with the read. Try holding the fob alone against the reader.
Note exactly what the reader does
A silent reader, one that beeps but does not unlock, and one that beeps with a different tone than usual all point to different faults, so this detail is genuinely useful information to pass on.
What Normally Causes It
The credential has been removed from the system
Fobs and cards are usually managed centrally, so a credential that was deleted, expired, or never correctly added after a staff change will be ignored by every reader on site, even though it looks and feels no different to a working one.
Physical damage to the fob or card
The antenna coil inside a fob is thin and can fracture if the fob is dropped repeatedly, bent, or put through a washing machine, silently killing the credential without any visible sign on the casing.
A failing or dirty reader
Readers mounted outdoors are exposed to weather and grime that can eventually affect the sensing coil behind the fascia, leading to a shorter read range or complete failure to detect any credential presented to it.
A loose connection between the reader and controller
The cable run from an external reader back to the access controller can work loose at the terminal block, particularly on doors that see heavy daily traffic, causing intermittent or total loss of reads.
Time or schedule restrictions on that credential
Many access systems allow fobs to be restricted to certain days or hours. A fob that stopped working exactly at a set time each day may simply be outside its permitted access schedule rather than faulty.
A controller or software fault affecting the whole site
If several unrelated fobs fail at the same reader or across multiple doors simultaneously, the controller itself or the software managing credentials may have lost synchronisation, which needs specialist diagnosis.
When to Stop and Call an Engineer
Keeping it from coming back
Keep spare fobs available for staff, avoid washing fobs or storing them loose with keys, and have the credential database reviewed periodically so leavers are removed and access schedules stay accurate.
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Frequently Asked Questions
Access Control Troubleshooting: Fob or Card Not Working: common questions
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