If the plant is healthy enough to withstand to be pruned to the base, cut down all existing growth in early spring to within 30-60 cm of the ground. To promote rapid new growth, apply a dressing of quick-acting, balanced fertilizer. Soak the root area with water and water the plant over the dry spells. Mulch the root area to conserve moisture. When the new shoots appear train them as for a newly planted climber.
If your climber is too old and you need to apply a two to three year renovation than you must be very patient as this job is more difficult than the first type of renovation because the stems of the plant frequently become entangled. Start the job in late winter or early spring removing as much congested growth as possible. Then cut to the base one in every two or three main stems. Gently unravel the top-growth of the several stems and if any shoots are damaged cut them out once the pruned main stems and their top-growth have been removed.
Continue with a general cleaning by removing any weak, spindly shoots and any dead wood. Help the plant to recover and to encourage the healthy new growth by feeding, watering and mulching it as you would do when pruning the plant to the base. Train in fresh basal shoots to fill the gaps, making sure they do not become entangled with the old shoots. The following spring repeat the process with the remained old main stems or with a part of them if you are going to repeat the process in the third year. Again feed, water and mulch the plant to help it recover and to promote now strong growth.