Adjustment options vary by model. A suitable closer can be checked within its permitted range, but stiffness may also relate to hinges, alignment or seals. The enquiry should describe the movement rather than assume turning an adjustment screw is the complete repair.
The last part of the closing movement should be checked with the ordinary latch and frame. Increasing force is not a substitute for correcting an incompatible or misaligned latch. Any separate hinge or hardware repair needs agreement before extending the closer task.
A closer needs to suit the door it controls. Provide leaf dimensions and product weight where available. An oversized or undersized unit should not be compensated for with extreme adjustment, and unsupported heavy doors need a different handling assessment.
Install a suitable ordinary supplied surface closer, make permitted adjustments or replace an unsuitable leaking unit within the agreed scope. Scope limits: Ordinary non-rated surface-mounted mechanical units only. No fire, smoke or egress certification, powered systems, structural reinforcement or specialist mechanisms.