Sky says affected boxes don't pose a safety risk to customers
Thousands of Sky+ HD customers are to have their boxes replaced after a fault was discovered by manufacturer Pace.
Ninety-thousand people, about one in 10 HD customers, will be affected.
Sky says the fault involves the internal cabling and the quality of the connections between components but is not a safety risk.
Anyone affected is also being given three months' free subscription to Sky's HD pack, worth £29.25, when they have their box replaced.
The 90,000 boxes in the first batch from Pace are model numbers 9F3001, 9F3002, 9F3003 and 9F3004.
Sky says the replacement programme will take about three months.
A statement on the Sky website said: "The assembly flaw does not involve a faulty component, such as a hard drive, or a software problem.
"Importantly, Pace has confirmed that the assembly flaw does not pose a safety risk.
"The box can continue to be used in the normal way, as installed by a Sky engineer, until we come to replace it."