Ours is the Carlton 3100 model. I've just managed to fix it by cleaning the vent to the outside of the house. We've always kept the lint filter clean - the one that slides in and out of the machine, in a slot between the drum and the door. What I hadn't realised until I tried cleaning it was that lint also builds up against a wire mesh fitted inside the plastic cover on the outside of the house - the other end of the flexible ventilation pipe. I think what happened to us was that the vent was blocked, the dryer couldn't get rid of the warm air fast enough, and the thermostat did what it's there for, turning the heat off to prevent a fire. Oh, and the sticky label underneath the dryer says it was made in 1988.
Joyce Whitchurch, November 2017