They must be old if they have a fuse link. These links are designed to melt to prevent the heater from overheating and to keep changing the fused links must cost a bit. Bite the bullet and buy some new Creda TSR Sensor Plus heaters. They are much more efficient, retain the heat all day and night and cost less to run than your old ones. I have them and have had no trouble at all with them. Once you get your desired heat that you require, they don't need to be touched again.
Homer, October 2010
