I keep reading about sticking valve pins in TRVs which can be freed up by pushing/tapping the valve pin. In decades of TRV usage I've never had this problem but after about 7/8 years the spring breaks which means the valve will only open (under spring pressure) a small amount leading to poor performance, the pin can easily be pulled out fully but will then revert to its small opening after one operation. The one attached is from a 7 year old EPH make that I changed today.
