I have an on going problem with sticking danfos rad valves (thermostatic type) causing radiators to stay cold. I can usually get them working with a sharp tap with a hammer but this is not a satisfactory method. I have also tried WD40 but to no avail. Any suggestions please?

Frank Picken, December 2004

There is no permanant repair or method to overcome this problem.
Replace them with more modern TRV's

Eric, December 2004