The fault locator was a component of the TARDIS.
History[]
The fault locator was located in the computer banks lining the console room wall and was used to detect the source of malfunctions on the ship.
When the TARDIS failed to dematerialise from Skaro, Susan Foreman checked the fault locator and determined that one of the fluid links, K7, had run out of mercury. (TV: "The Dead Planet" [+]Part of The Daleks, Terry Nation, Doctor Who season 1 (BBC tv, 1963-1964).)
After the Doctor had disabled a static electricity relay box in the Dalek City, Susan warned that the Daleks must have their own fault locator somewhere, before both were ambushed by Daleks. (TV: "The Ordeal" [+]Part of The Daleks, Terry Nation, Doctor Who season 1 (BBC tv, 1963-1964).)
Shortly afterwards, when the fast return switch became stuck, the fault locator could not indicate the source of the problem as the switch was not broken, merely stuck. To warn the crew of the danger, the TARDIS had the fault locator completely lit up, indicating that every system was breaking down. The lights on the locator flashed every fifteen seconds, indicating that the ship would be destroyed in fifteen minutes. (TV: "The Brink of Disaster" [+]Part of The Edge of Destruction, David Whitaker, Doctor Who season 1 (BBC tv, 1964).)
Later, the Doctor and Barbara examined the fault locator when trying to determine what had them stranded on Luxor. They found nothing wrong, despite the power loss the TARDIS was experiencing. (AUDIO: The Masters of Luxor [+]Error: Code 2 - no data stored in variables, cache or SMW.)
Following the TARDIS crashing on Ashtallah, the fault locator registered seventeen broken systems. Susan noted however that most of these were self-repairing. (AUDIO: The Invention of Death [+]John Dorney, The First Doctor Adventures: Volume Two (The First Doctor Adventures, Big Finish Productions, 2018).)
Later still, the fault locator registered faults just before the TARDIS doors opened in mid-flight; however, after the TARDIS materialised, the fault locator indicated that nothing was wrong. (TV: Planet of Giants [+]Louis Marks, Doctor Who season 2 (BBC1, 1964).) It was much later revealed that it had broken down at some point but claimed it was working perfectly, which made repairs to it almost impossible. (PROSE: The Three Paths [+]Ian Potter, Short Trips: Farewells (Short Trips, 2006).)
When the TARDIS failed to change its location on Tiro, the Doctor checked the fault locator and determined that one of the klister valves had run out of magnatite. (PROSE: Terror on Tiro [+]The Dr Who Annual 1967 (Doctor Who annual, 1966).)
Brewster sold the crew of the Gamma the TARDIS' fault locator, along with the conceptual geometer, food machine and power lens unit. (AUDIO: Time Reef [+]Marc Platt, Main Range (Big Finish Productions, 2008).)
When the TARDIS warned the Seventh Doctor that it was in trouble, he first tried checking the fault locator, but it did not detect any malfunctions. He eventually realised that an alien creature was attempting to get into his ship. (PROSE: Cat's Cradle: Time's Crucible [+]Marc Platt, adapted from Cat's Cradle, Virgin New Adventures (Virgin Books, 1992).)
By the time that Susan and her son Alex joined the Eighth Doctor and Lucie in the TARDIS for Christmas, the fault locator had itself developed a fault. (AUDIO: Relative Dimensions [+]Marc Platt, Eighth Doctor Adventures (Big Finish Productions, 2010).)
Behind the scenes[]
- During rehearsals of The Edge of Destruction, William Hartnell said "fornicator" instead of "fault locator" as a gag for Carole Ann Ford. This did not make it into the finished product, but the story lasted long enough to be featured in the 2013 docu-drama An Adventure in Space and Time, portrayed here as one of Hartnell's "Billy-fluffs"