Plans to get Britain's first offshore wind farm producing power again after a gap of almost three years have been stalled by a further technical hitch.
Rotor blades on the two turbines off Cambois, Northumberland have not turned since March 2006, when the seabed cable connecting them to the mainland snapped.
Two months ago power company E.on said it was about to switch them on again after replacing the damaged cable.
Now it says it will be several weeks before the turbines are ready to become fully operational again, after a brief trial run revealed an internal technical problem which needs to be put right.
The turbines - built in 2000 to generate enough power to meet the needs of 3,000 homes - are now being fully serviced to ensure they are ready to go when switched back on permanently.
Yesterday an E.on spokeswoman said: "The seabed cabling has all been repaired and re-installed and we switched the turbines back on for a short period to warm them up, after they were off for more than two years. During the warm-up process we discovered an extra internal problem which is being fixed.
"They were off for a long time and got a bit damp inside so we are now doing a full service and hope to have them up and running again, and producing electricity, in the next few weeks.
"It has meant a delay in getting the blades turning again and we are dependent on the weather to get on and complete the service."
The two turbines were built at a cost of pounds 4m but have been out of action since the undersea power cable was snapped by the rocky seabed. Now E.on has replaced the cable, using a different route to allow sections of it to be buried in sand.
The two turbines were previously owned by a green power consortium. In 2002, a rotor blade had to be replaced after it was hit by lightning and in 2005 one of the turbines was out of action for several months after a cable connecting the two machines failed.