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Wiremap fail, crossed or reversed pairs

very common

“Tester throws a wiremap error. I've looked at both ends twice and the colors look right to me.”

Likely causes

  • T568A one end, T568B the other

    ~35%

    Wiremap shows pins 1,2 and 3,6 swapped end to end and everything else straight through. Almost never one run on its own: it repeats across every run one person did that shift.

  • Reversed pair (tip and ring flipped)

    ~25%

    Exactly two pins swapped and both belong to the same pair, usually 1/2 or 3/6. Classic on runs punched voice-style.

  • Open conductor

    ~20%

    Tester names the pins and gives a distance. Near 0 m is the end you're plugged into, at full link length is the far jack, anything in between is damage. Check the tester's own cord first.

  • Punched to the color code instead of the jack's printed sequence

    ~10%

    Identical fault on every jack of that brand or batch. Look at the jack body: the punch sequence rarely runs 1 to 8 left to right.

  • Short

    ~7%

    Short reported with a distance. A stray strand bridging at the punch reads 0 m; a screw or staple reads a repeatable mid-run distance you can pace out.

  • Coupler, surface box or unrecorded consolidation point in the path

    ~3%

    Measured length longer than the as-built, and the wiremap changes when that box is opened.

What to bring

  • Certifier with permanent link adapters
  • Spare test cords and adapter tips
  • Punch tool with correct blade
  • Jack instruction sheet (phone)
  • Inspection light
  • Tone generator and probe
  • Ladder or lift

Safety

Do not punch down or re-terminate a pair carrying PoE. Unplug the switch port first. A reused run is exactly where an unrecorded live port turns up on the far end, and breaking a loaded pair arcs and pits the contacts. Type 4 is four-pair by definition and Type 3 may be two-pair or four-pair, so assume all four pairs are live until the port is unplugged (IEEE 802.3 cl. 145). Ceiling work: ladder or lift discipline, and in pre-1980 buildings treat ceiling tile, fireproofing and pipe lagging as asbestos until it is cleared.

Steps

  1. Read the wiremap graphic, not the pass/fail

    Write down exactly which pins swap before you climb. 1,2 to 3,6 end to end is an A/B mix. Two pins of one pair is a reversal. An open or short comes with a distance.

    If that doesn’t do it

    If the graphic is clean and only the verdict is bad, you are looking at a limit or configuration problem, not a wiring one. Go to Whole job failing, or passing too well.

  2. Swap the tester's test cord or adapter and retest

    Free. Broken conductors in test cords and worn adapter tips produce opens that look like field faults, and they show on every link, not one.

    If that doesn’t do it

    Fault stays on this link only: it is in the building. Continue.

  3. Find out from the paperwork which pinout the job was built to

    A and B are both legal; mixing them is not. The certifier cannot tell you which was used: A and B links are pin-for-pin identical, so a consistent A-to-A or B-to-B job passes wiremap the same. Get it from the as-built and from the other runs on the job.

    If that doesn’t do it

    Scheme is documented and consistent: open both ends and read colours against pins.

  4. Open the outlet end first

    Head height, and it's where the fault usually is. What holds in both A and B: 4,5 is always the blue pair, 7,8 always brown, and 1,2 and 3,6 must each carry both conductors of one pair. Orange on 3,6 in A, green on 3,6 in B. Cap fully closed, no conductor short of the contact.

    If that doesn’t do it

    Outlet is correct: go to the panel end.

  5. Re-punch to the jack's own instruction sheet

    Unplug the switch port first. Sequence off the jack body, not memory. Keep the sheath as long as the jack allows and untwist as little as possible. About 13 mm is the working figure on Cat5e; Cat6 and 6A follow the jack sheet, usually much less.

    If that doesn’t do it

    Both ends re-punched and it still maps wrong: the fault is in the cable.

  6. Use the distance the tester gave you

    Pace out the distance and inspect. Staples, screws through the sheath, tray edges, pinch points at firestop sleeves. Compare measured length against the label length while you are there.

    If that doesn’t do it

    No damage found at the distance: suspect a hidden block, CP or coupler in the path.

  7. Replace the damaged section or re-pull

    One damaged conductor is not repairable to category. Re-pull the run and re-certify.

    If that doesn’t do it

    New run fails the same way: you have the wrong run identified. Tone it out and re-label.

References

  • ANSI/TIA-568.2-D cl. 6 (field test requirements)
  • ANSI/TIA-568.1-D cl. 6 (horizontal cabling)
  • ANSI/TIA-606-C (identification and as-built records)

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