The 127-year-old bridge was closed in both directions to traffic on Thursday.
The latest fault comes after the bridge was closed for several hours in August after the bridge’s arms, known as bascules, became wedged upright after being opened.
A tweet by City of London Police said: “Tower Bridge is currently closed to traffic and pedestrians due to technical failure. Please avoid the area. Updates to follow.”
In August this year the bridge became stuck after allowing a Jubilee Trust Tall Ship to pass beneath it.
Engineers worked through the night and managed to close the bridge before the following morning’s rush hour.
In 2020 the bridge failed to close after allowing a ship to pass along the River Thames. Hundreds of motorists and pedestrians were left waiting for at least an hour from both directions.
Also in 2005 police closed the bridge for ten hours after a technical problem prevented the arms from being lowered.
Each of its bascules weigh more than 1,100 tons each with a 400 ton counterweight to help them descend after lifting to allow river traffic to pass through.
Construction began on the bridge in 1886 on a design by City of London architect Sir Horace Jones.
It was opened in 1894 by Edward VII and his wife Alexandra of Denmark, then the Prince and Princess of Wales, along with future Prime Minister Herbert Henry Asquith - then Home Secretary.