i have hattersley thermostatic radiator valves i have read the other peoples comments about getting the collar off to get to the pin i do have a hole under the collar but cannot see a allen screw or grub screw the rads are about 20 years old but five are working the bathroom and upstairs landing ones are not heating up any help please would be very much appreciated.

dave., October 2010

The collars usually unscrew upwards but stay attached - you don't remove them - as the collar moves upwards it allows the whole piece to be gently wriggled off.

My plumber says do not pull up on the pin with pliers but give it gentle taps with the side of a spanner or pliers until it rises on its own.

Peccavi, October 2010