Some time the heads on the TRV is broken and doesn't move ehrn you change the setting it is on. Try replacing the head, otherwise the radiations will need to be re balanced. Switch off all the other radiators and leave the one that is cold on. If it heats open all the other radiators one at a time a quater turn. If the radiator starts cooling down shut the valve of that radiator slightly and continue with the radiator where you left
Simon
March 2009