The lights on Blackpool Tower are set to be replaced as part of a £200,000 investment - but it means parts of the famous landmark will be in the dark during this year's Illuminations.
Only the legs facing the sea and the top of the Tower will be lit this year - along with the giant heart on the front of the structure which has already been refitted with new-style light nodes.
It is planned to fit the rest of the Tower with the upgraded lights over the next 18 months if the trials on the heart display prove successful.
The aim of the project is to find a more durable system which is better at withstanding severe weather conditions.
It is hoped the bulk of the Tower, which is 125 years old this year, will have newly fitted lights in time for next year's Illuminations.
Coun Gillian Campbell, deputy leader of Blackpool Council, said: “The lighting on the Tower has to be constantly maintained simply because of the beachfront location and severe weather conditions that often come in from the Irish Sea.
“For this season, we are trialing a new form of lighting nodes on the heart to determine how much better they stand up to the conditions.
“That work has now been completed and the heart reinstalled on the front of the Tower.
"It looks fantastic and we are delighted it is in place for this milestone anniversary year along with the lighting on the west face and the Tower top.
“It is a little disappointing that we cannot light up the whole of the Tower for the coming Illuminations season, but replacement of lighting on such a large scale structure cannot be achieved overnight.”
Kate Shane, head of the Merlin cluster of attractions in Blackpool including the Tower, said: "The work that has been done on the new system for the giant heart looks amazing and the Switch-on was spectacular.
"But the old kit is up to 500ft in the air and there are 100mph wind gusts at times so the elements are quite severe.
"Everyone in Blackpool is proud of the Tower and we want to be able to light it with a system that is robust enough to cope with conditions.
"It's a lengthy task and so it means for this season we will have only one side lit, but the Tower will soon be back to its full resplendent glory."
Claire Smith, president of hoteliers group StayBlackpool, said: "People have said the Illuminations are fabulous but they have noticed the Tower is not fully lit.
"I'm pleased the council is telling us what is happening so we can pass that information on to visitors.
"Hopefully the work can be done sooner rather than later as it's vital the Tower is fully lit again."
The £200,000 cost is being met from a council sink fund set up to maintain and improve the Tower buildings. It would cost a similar amount of money to maintain the existing LEDs which have been continually replaced due to weather damage.
The last time the lights on the Tower were replaced was in 2011 when 10,000 old pygmy bulbs were replaced with more efficient LED lights as part of a £250,000 refurbishment programme.