Badly installed network

Had an emergency call out to a local supermarket today, their network had gone down making their tills inoperative.

When I arrived, there was a long patch cable strung across the shop floor to the point of sale terminals. The manager informed me that they had previously had an engineer in who said there was nothing wrong with the wiring.

Normally I attempt to repair before re-wiring (this is an 'open all hours' supermarket and removing ceiling tiles to re-lay the cable or pull new cable using the existing would have been extremely disruptive requiring dismantling of much of their counter displays). Hooking up the network tester to the two points revealed that one had two wires reversed on the cable and another was showing open circuits across two pairs. Opening up the Cat 5 outlet behind the till revealed two wires that had not been punched down correctly and examining the RJ45 connectors in the back office revealed the one which the owners had been informed was damaged during installation had in fact been wired incorrectly.

All in all the diagnosis and repair took about 20 minutes which was much less disruptive than re-cabling.