Any Plumbers out there, when we turn the shower on the fitting is very stiff and very little water comes out, when we take off the fitting and turn the cogs by hand it's fine, we need to know if replacing the cartridge will fix the problem, don't want to spend money replacing parts if we need to get a plumber in.
Heat regulator is fine just the on off control.
Thanks in advance
Get an overhaul seal kit for your make and model of shower.
Usually available, and worth doing.
Sounds like seals hardened and worn, or coated in scale.