I have had loads of problems with heaters, have bought a few on e-bay and all have stopped working or cooked my fish. The only heaters i havn't had problems with are the 'Elite' heaters, they cost a bit more but are worth every penny ( i now have them in both my big tanks ).
I'm beginning to suspect the thermometer. I've had both heaters in a bucket of water overnight and the thermometer says the water is 21 but it feels really quite warm to me. So I'm going to get another thermometer today and see what that says. Thanks for your advice!
We bought a Juwel 60litre tank for our daughter about three weeks ago and all was fine for the first week or so, but then the temperature dropped from 26 to 19. We assumed it was the heater and got a new one sent to us, but that one doesn't seem to work either! We have them in a bucket now, and they are warm, but not hot. Do you know, should they be hot to the touch? And if they are not the problem, then what could it be?? I'm beginning to wish we'd never started this!