Day to day here at R3, lots of head swaps are done on jobs that we have in with us. When a drive requires a head swap it means that the read/write heads that are in the drive currently are either failing or have failed. Every hard drive will fail at some point, whether it's due to it being dropped or it's an age related issue, or even an overheating issue, all drives ultimately will fail.
But when a head swap is done, technically the drive is then in a working condition. However, it is not in a stable condition, all drives that have had a head swap require to be monitored as the engineers don't know how well the drive/heads will react to having a foreign part being used instead of the original. Furthermore not all head swaps work, even though the technicians who match the parts are efficient. For instance they can get a perfectly matching donor that in all most every aspect matches the original drive, but then after opening the drive the heads inside are not always compatible and will not work no matter what the engineers do.
When a head swap does work on the other hand the engineers can have full control over the drive; how fast it reads, the option to disable certain heads, the list goes on. As a user this is impossible to do which again is another reason why a drive that's had a head swap cannot just be simply put back into a laptop for example. Also in some circumstances the engineers may have to disable certain read/write heads in the drive, this is normally because the surface that the head is reading is incredible damaged and is slowing down the cloning speed. After the good surfaces are cloned the engineers go back to the damaged areas of the drive and read them as slow as possible as this is one of the only ways damaged areas of the drive can be recovered.
In short when a drive has a head swap it is not in a stable condition like it was when it was first manufactured. However it is in a stable enough state for our expert engineers to get the data of the drive for the customer.
If you have a drive that is making a clicking noise and you think it is mechanically failed get in contact with us here at R3. Talk to our data recovery technicians at 0800 999 3282 and get immediate help and advice.