Read range short at one reader

Likely causes

• Reader mounted straight onto metal with no spacer

  ~28%

  Range collapses at this door and only this door, and the reader is on a hollow metal frame, a mullion, or a metal back box. Most OEMs publish a spacer or a metal-mount variant for exactly this; a mullion reader is designed for it, a wall reader usually is not.

• Two readers too close: back to back through a wall, or crowded on one mullion

  ~20%

  Both doors read badly, and one improves the moment the other is powered down. OEMs publish a minimum separation per model, and both faces of a single wall count as close.

• Interference from equipment behind or beside the reader

  ~18%

  LED drivers, switching supplies, monitors, digital signage, EV chargers, VFDs. Kill the suspected load and the range comes back. Low-frequency 125 kHz prox suffers worst. Test at different times of day: the offender may be on a timer.

• Reader power sagging at the moment of read

  ~12%

  Range is worse when the door is busy or when a lock fires. Go to Reader dead: no light, no beep for the voltage check and Reader resets when the lock pulls if it tracks the lock.

• Credential type and its own range

  ~10%

  A clamshell, a moulded fob, a smart card and a phone all read at different distances by design, and a card in a wallet behind another card reads worse. Test with one known-good card of the site's type, held flat and square.

• Reader failing, water damaged, or antenna degraded

  ~7%

  Swap clears it with nothing else changed. Look for water staining, a swollen face, or corrosion on the pigtail.

• Range or power setting turned down in configuration

  ~5%

  Config readback shows a reduced range or low-power mode, often set deliberately to stop cross-reads between two close readers, then forgotten by everyone.

What to bring

• Known-good card of the site's type
• Tape measure or a marked card holder
• DMM
• Known-good reader
• OEM installation sheet and spacer part numbers
• Reader config app or config cards
• Ladder

Steps

1. 1

   Step 1: Measure the range you actually have, in one plane

   Same card, held flat, square to the face, approaching straight in. Write down the distance and compare it to the reader's published figure and to a healthy reader on the same site. 'Bad range' is not a measurement.

   If that doesn’t do it

   Take the reader off the wall.

2. 2

   Step 2: Pull the reader off the wall and try it on a lead, held in free air

   Full range in your hand and nothing on the wall is the whole answer: it is the mounting surface or what's behind it, not the reader. This one move saves most of these calls.

   If that doesn’t do it

   Range is still short in free air: check power, then the credential, then swap the reader.

3. 3

   Step 3: Look at what is behind and beside the reader

   Metal frame or box, conduit, structural steel, and anything electronic on the other side of that wall. Ask what is in the room behind the door: signage and monitors get installed long after the reader.

   If that doesn’t do it

   Power down the suspects one at a time.

4. 4

   Step 4: Power down suspected interferers one at a time

   With the owner's permission and never a life-safety load. Range returning as one load drops names it. Both the reader and the interferer are Part 15 devices: neither has a right to a quiet spectrum, so the fix is separation or shielding, not an argument.

   If that doesn’t do it

   Check reader-to-reader separation.

5. 5

   Step 5: Check the separation between readers against the OEM's minimum

   Per model, and count the reader on the far side of the wall. Under the minimum, the fix is to move one reader, offset them vertically, or fit the OEM's shielding, not to turn the range down until nothing works.

   If that doesn’t do it

   Fit the spacer or the right variant.

6. 6

   Step 6: Fit the OEM spacer, or change to the metal-mount variant

   This is a parts answer, and it is cheap compared with the truck rolls it prevents. Get the part number off the reader's own installation sheet.

   If that doesn’t do it

   Read the reader's range and power configuration.

7. 7

   Step 7: Read the reader's own range setting before you condemn it

   Pull the config via config card, app or OSDP. If somebody reduced the range on purpose, find out why before you put it back: it was probably solving the cross-read problem at the door next to you.

   If that doesn’t do it

   Swap the reader and re-measure the same way.

More Access Control guides

• Reader dead: no light, no beep
• Valid read, door never unlocks
• Denied at certain times or certain doors
• Card works at one door, not another
• Nuisance door held and forced alarms
• Intermittent reads and ghost reads on Wiegand
• Keypad won't take the PIN

All 54 guides